Find, fix and prevent vulnerabilities in your code.
high severity
new
- Vulnerable module: qs
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › qs@0.6.6Remediation: Upgrade to express@4.0.0.
Overview
qs is a querystring parser that supports nesting and arrays, with a depth limit.
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling via improper enforcement of the arrayLimit option in bracket notation parsing. An attacker can exhaust server memory and cause application unavailability by submitting a large number of bracket notation parameters - like a[]=1&a[]=2 - in a single HTTP request.
PoC
const qs = require('qs');
const attack = 'a[]=' + Array(10000).fill('x').join('&a[]=');
const result = qs.parse(attack, { arrayLimit: 100 });
console.log(result.a.length); // Output: 10000 (should be max 100)
Remediation
Upgrade qs to version 6.14.1 or higher.
References
high severity
- Vulnerable module: xmlhttprequest
- Introduced through: socket.io@0.9.19
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › socket.io@0.9.19 › socket.io-client@0.9.16 › xmlhttprequest@1.4.2Remediation: Upgrade to socket.io@1.0.1.
Overview
xmlhttprequest is a wrapper for the built-in http client to emulate the browser XMLHttpRequest object.
Affected versions of this package are vulnerable to Arbitrary Code Injection. Provided requests are sent synchronously (async=False on xhr.open), malicious user input flowing into xhr.send could result in arbitrary code being injected and run.
POC
const { XMLHttpRequest } = require("xmlhttprequest")
const xhr = new XMLHttpRequest()
xhr.open("POST", "http://localhost.invalid/", false /* use synchronize request */)
xhr.send("\\');require(\"fs\").writeFileSync(\"/tmp/aaaaa.txt\", \"poc-20210306\");req.end();//")
Remediation
Upgrade xmlhttprequest to version 1.7.0 or higher.
References
high severity
- Vulnerable module: fresh
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › fresh@0.2.0Remediation: Upgrade to express@4.15.5.
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › send@0.1.4 › fresh@0.2.0Remediation: Upgrade to express@4.15.5.
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › fresh@0.2.0Remediation: Upgrade to express@4.0.0.
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › send@0.1.4 › fresh@0.2.0Remediation: Upgrade to express@4.0.0.
Overview
fresh is HTTP response freshness testing.
Affected versions of this package are vulnerable to Regular expression Denial of Service (ReDoS) attacks. A Regular Expression (/ *, */) was used for parsing HTTP headers and take about 2 seconds matching time for 50k characters.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
AThe string must start with the letter 'A'(B|C+)+The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+matches one or more times). The+at the end of this section states that we can look for one or more matches of this section.DFinally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
| String | Number of C's | Number of steps |
|---|---|---|
| ACCCX | 3 | 38 |
| ACCCCX | 4 | 71 |
| ACCCCCX | 5 | 136 |
| ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade fresh to version 0.5.2 or higher.
References
high severity
- Vulnerable module: negotiator
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › negotiator@0.3.0Remediation: Upgrade to express@4.0.0.
Overview
negotiator is an HTTP content negotiator for Node.js.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS)
when parsing Accept-Language http header.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
AThe string must start with the letter 'A'(B|C+)+The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+matches one or more times). The+at the end of this section states that we can look for one or more matches of this section.DFinally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
| String | Number of C's | Number of steps |
|---|---|---|
| ACCCX | 3 | 38 |
| ACCCCX | 4 | 71 |
| ACCCCCX | 5 | 136 |
| ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade negotiator to version 0.6.1 or higher.
References
high severity
- Vulnerable module: qs
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › qs@0.6.6Remediation: Upgrade to express@3.16.0.
Overview
qs is a querystring parser that supports nesting and arrays, with a depth limit.
Affected versions of this package are vulnerable to Denial of Service (DoS).
During parsing, the qs module may create a sparse area (an array where no elements are filled), and grow that array to the necessary size based on the indices used on it. An attacker can specify a high index value in a query string, thus making the server allocate a respectively big array. Truly large values can cause the server to run out of memory and cause it to crash - thus enabling a Denial-of-Service attack.
Remediation
Upgrade qs to version 1.0.0 or higher.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.
Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.
One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.
When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.
Two common types of DoS vulnerabilities:
High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.
Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm
wspackage
References
high severity
- Vulnerable module: qs
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › qs@0.6.6Remediation: Upgrade to express@4.0.0.
Overview
qs is a querystring parser that supports nesting and arrays, with a depth limit.
Affected versions of this package are vulnerable to Prototype Override Protection Bypass. By default qs protects against attacks that attempt to overwrite an object's existing prototype properties, such as toString(), hasOwnProperty(),etc.
From qs documentation:
By default parameters that would overwrite properties on the object prototype are ignored, if you wish to keep the data from those fields either use plainObjects as mentioned above, or set allowPrototypes to true which will allow user input to overwrite those properties. WARNING It is generally a bad idea to enable this option as it can cause problems when attempting to use the properties that have been overwritten. Always be careful with this option.
Overwriting these properties can impact application logic, potentially allowing attackers to work around security controls, modify data, make the application unstable and more.
In versions of the package affected by this vulnerability, it is possible to circumvent this protection and overwrite prototype properties and functions by prefixing the name of the parameter with [ or ]. e.g. qs.parse("]=toString") will return {toString = true}, as a result, calling toString() on the object will throw an exception.
Example:
qs.parse('toString=foo', { allowPrototypes: false })
// {}
qs.parse("]=toString", { allowPrototypes: false })
// {toString = true} <== prototype overwritten
For more information, you can check out our blog.
Disclosure Timeline
- February 13th, 2017 - Reported the issue to package owner.
- February 13th, 2017 - Issue acknowledged by package owner.
- February 16th, 2017 - Partial fix released in versions
6.0.3,6.1.1,6.2.2,6.3.1. - March 6th, 2017 - Final fix released in versions
6.4.0,6.3.2,6.2.3,6.1.2and6.0.4
Remediation
Upgrade qs to version 6.0.4, 6.1.2, 6.2.3, 6.3.2 or higher.
References
high severity
- Vulnerable module: qs
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › qs@0.6.6Remediation: Upgrade to express@4.0.0.
Overview
qs is a querystring parser that supports nesting and arrays, with a depth limit.
Affected versions of this package are vulnerable to Prototype Poisoning which allows attackers to cause a Node process to hang, processing an Array object whose prototype has been replaced by one with an excessive length value.
Note: In many typical Express use cases, an unauthenticated remote attacker can place the attack payload in the query string of the URL that is used to visit the application, such as a[__proto__]=b&a[__proto__]&a[length]=100000000.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.
Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.
One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.
When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.
Two common types of DoS vulnerabilities:
High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.
Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm
wspackage
Remediation
Upgrade qs to version 6.2.4, 6.3.3, 6.4.1, 6.5.3, 6.6.1, 6.7.3, 6.8.3, 6.9.7, 6.10.3 or higher.
References
high severity
- Vulnerable module: ws
- Introduced through: socket.io@0.9.19
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › socket.io@0.9.19 › socket.io-client@0.9.16 › ws@0.4.32Remediation: Upgrade to socket.io@1.0.1.
Overview
ws is a WebSocket client and server implementation.
Affected versions of this package did not limit the size of an incoming payload before it was processed by default. As a result, a very large payload (over 256MB in size) could lead to a failed allocation and crash the node process - enabling a Denial of Service attack.
While 256MB may seem excessive, note that the attack is likely to be sent from another server, not an end-user computer, using data-center connection speeds. In those speeds, a payload of this size can be transmitted in seconds.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.
Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.
One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.
When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.
Two common types of DoS vulnerabilities:
High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.
Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm
wspackage
Remediation
Update to version 1.1.1 or greater, which sets a default maxPayload of 100MB.
If you cannot upgrade, apply a Snyk patch, or provide ws with options setting the maxPayload to an appropriate size that is smaller than 256MB.
References
high severity
- Vulnerable module: ws
- Introduced through: socket.io@0.9.19
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › socket.io@0.9.19 › socket.io-client@0.9.16 › ws@0.4.32Remediation: Upgrade to socket.io@1.0.1.
Overview
ws is a simple to use websocket client, server and console for node.js.
Affected versions of this package are vulnerable to Denial of Service (DoS)
attacks. A specially crafted value of the Sec-WebSocket-Extensions header that used Object.prototype property names as extension or parameter names could be used to make a ws server crash.
PoC:
const WebSocket = require('ws');
const net = require('net');
const wss = new WebSocket.Server({ port: 3000 }, function () {
const payload = 'constructor'; // or ',;constructor'
const request = [
'GET / HTTP/1.1',
'Connection: Upgrade',
'Sec-WebSocket-Key: test',
'Sec-WebSocket-Version: 8',
`Sec-WebSocket-Extensions: ${payload}`,
'Upgrade: websocket',
'\r\n'
].join('\r\n');
const socket = net.connect(3000, function () {
socket.resume();
socket.write(request);
});
});
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.
Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.
One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.
When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.
Two common types of DoS vulnerabilities:
High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.
Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm
wspackage
Remediation
Upgrade ws to version 1.1.5, 3.3.1 or higher.
References
medium severity
- Vulnerable module: qs
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › qs@0.6.6Remediation: Upgrade to express@3.16.0.
Overview
qs is a querystring parser that supports nesting and arrays, with a depth limit.
Affected versions of this package are vulnerable to Denial of Service (DoS). When parsing a string representing a deeply nested object, qs will block the event loop for long periods of time. Such a delay may hold up the server's resources, keeping it from processing other requests in the meantime, thus enabling a Denial-of-Service attack.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
AThe string must start with the letter 'A'(B|C+)+The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+matches one or more times). The+at the end of this section states that we can look for one or more matches of this section.DFinally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
| String | Number of C's | Number of steps |
|---|---|---|
| ACCCX | 3 | 38 |
| ACCCCX | 4 | 71 |
| ACCCCCX | 5 | 136 |
| ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade qs to version 1.0.0 or higher.
References
medium severity
- Vulnerable module: ws
- Introduced through: socket.io@0.9.19
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › socket.io@0.9.19 › socket.io-client@0.9.16 › ws@0.4.32Remediation: Upgrade to socket.io@1.0.1.
Overview
ws is a simple to use websocket client, server and console for node.js.
Affected versions of the package are vulnerable to Uninitialized Memory Exposure.
A client side memory disclosure vulnerability exists in ping functionality of the ws service. When a client sends a ping request and provides an integer value as ping data, it will result in leaking an uninitialized memory buffer.
This is a result of unobstructed use of the Buffer constructor, whose insecure default constructor increases the odds of memory leakage.
ws's ping function uses the default Buffer constructor as-is, making it easy to append uninitialized memory to an existing list. If the value of the buffer list is exposed to users, it may expose raw memory, potentially holding secrets, private data and code.
Proof of Concept:
var ws = require('ws')
var server = new ws.Server({ port: 9000 })
var client = new ws('ws://localhost:9000')
client.on('open', function () {
console.log('open')
client.ping(50) // this makes the client allocate an uninitialized buffer of 50 bytes and send it to the server
client.on('pong', function (data) {
console.log('got pong')
console.log(data)
})
})
Details
The Buffer class on Node.js is a mutable array of binary data, and can be initialized with a string, array or number.
const buf1 = new Buffer([1,2,3]);
// creates a buffer containing [01, 02, 03]
const buf2 = new Buffer('test');
// creates a buffer containing ASCII bytes [74, 65, 73, 74]
const buf3 = new Buffer(10);
// creates a buffer of length 10
The first two variants simply create a binary representation of the value it received. The last one, however, pre-allocates a buffer of the specified size, making it a useful buffer, especially when reading data from a stream.
When using the number constructor of Buffer, it will allocate the memory, but will not fill it with zeros. Instead, the allocated buffer will hold whatever was in memory at the time. If the buffer is not zeroed by using buf.fill(0), it may leak sensitive information like keys, source code, and system info.
Similar vulnerabilities were discovered in request, mongoose, ws and sequelize.
References
medium severity
- Vulnerable module: cookie
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › cookie@0.1.0Remediation: Upgrade to express@4.21.1.
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › cookie@0.1.0Remediation: Upgrade to express@4.0.0.
Overview
Affected versions of this package are vulnerable to Cross-site Scripting (XSS) via the cookie name, path, or domain, which can be used to set unexpected values to other cookie fields.
Workaround
Users who are not able to upgrade to the fixed version should avoid passing untrusted or arbitrary values for the cookie fields and ensure they are set by the application instead of user input.
Details
Cross-site scripting (or XSS) is a code vulnerability that occurs when an attacker “injects” a malicious script into an otherwise trusted website. The injected script gets downloaded and executed by the end user’s browser when the user interacts with the compromised website.
This is done by escaping the context of the web application; the web application then delivers that data to its users along with other trusted dynamic content, without validating it. The browser unknowingly executes malicious script on the client side (through client-side languages; usually JavaScript or HTML) in order to perform actions that are otherwise typically blocked by the browser’s Same Origin Policy.
Injecting malicious code is the most prevalent manner by which XSS is exploited; for this reason, escaping characters in order to prevent this manipulation is the top method for securing code against this vulnerability.
Escaping means that the application is coded to mark key characters, and particularly key characters included in user input, to prevent those characters from being interpreted in a dangerous context. For example, in HTML, < can be coded as < and > can be coded as > in order to be interpreted and displayed as themselves in text, while within the code itself, they are used for HTML tags. If malicious content is injected into an application that escapes special characters and that malicious content uses < and > as HTML tags, those characters are nonetheless not interpreted as HTML tags by the browser if they’ve been correctly escaped in the application code and in this way the attempted attack is diverted.
The most prominent use of XSS is to steal cookies (source: OWASP HttpOnly) and hijack user sessions, but XSS exploits have been used to expose sensitive information, enable access to privileged services and functionality and deliver malware.
Types of attacks
There are a few methods by which XSS can be manipulated:
| Type | Origin | Description |
|---|---|---|
| Stored | Server | The malicious code is inserted in the application (usually as a link) by the attacker. The code is activated every time a user clicks the link. |
| Reflected | Server | The attacker delivers a malicious link externally from the vulnerable web site application to a user. When clicked, malicious code is sent to the vulnerable web site, which reflects the attack back to the user’s browser. |
| DOM-based | Client | The attacker forces the user’s browser to render a malicious page. The data in the page itself delivers the cross-site scripting data. |
| Mutated | The attacker injects code that appears safe, but is then rewritten and modified by the browser, while parsing the markup. An example is rebalancing unclosed quotation marks or even adding quotation marks to unquoted parameters. |
Affected environments
The following environments are susceptible to an XSS attack:
- Web servers
- Application servers
- Web application environments
How to prevent
This section describes the top best practices designed to specifically protect your code:
- Sanitize data input in an HTTP request before reflecting it back, ensuring all data is validated, filtered or escaped before echoing anything back to the user, such as the values of query parameters during searches.
- Convert special characters such as
?,&,/,<,>and spaces to their respective HTML or URL encoded equivalents. - Give users the option to disable client-side scripts.
- Redirect invalid requests.
- Detect simultaneous logins, including those from two separate IP addresses, and invalidate those sessions.
- Use and enforce a Content Security Policy (source: Wikipedia) to disable any features that might be manipulated for an XSS attack.
- Read the documentation for any of the libraries referenced in your code to understand which elements allow for embedded HTML.
Remediation
Upgrade cookie to version 0.7.0 or higher.
References
medium severity
- Vulnerable module: cookie-signature
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › cookie-signature@1.0.1Remediation: Upgrade to express@3.12.1.
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › cookie-signature@1.0.1Remediation: Upgrade to express@3.12.1.
Overview
'cookie-signature' is a library for signing cookies.
Versions before 1.0.4 of the library use the built-in string comparison mechanism, ===, and not a time constant string comparison. As a result, the comparison will fail faster when the first characters in the token are incorrect.
An attacker can use this difference to perform a timing attack, essentially allowing them to guess the secret one character at a time.
You can read more about timing attacks in Node.js on the Snyk blog: https://snyk.io/blog/node-js-timing-attack-ccc-ctf/
Remediation
Upgrade to 1.0.4 or greater.
References
medium severity
- Vulnerable module: express
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8Remediation: Upgrade to express@4.0.0.
Overview
express is a minimalist web framework.
Affected versions of this package are vulnerable to Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') through the response.links function. An attacker can inject arbitrary resources into the Link header by using unsanitized input that includes special characters such as commas, semicolons, and angle brackets.
PoC
var express = require('express')
var app = express()
app.get('/', function (req, res) {
res.links({"preload": req.query.resource});
if(req.query.resource){
console.log(res.getHeaders().link)
}
res.send('ok');
});
app.listen(3000);
// note how the query param uses < > to load arbitrary resource
const maliciousQueryParam = '?resource=http://api.example.com/users?resource=>; rel="preload", <http://api.malicious.com/1.js>; rel="preload"; as="script", <http:/api.example.com';
const url = `http://localhost:3000/${maliciousQueryParam}`;
fetch(url);
Remediation
Upgrade express to version 4.0.0-rc1 or higher.
References
medium severity
- Vulnerable module: express
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8Remediation: Upgrade to express@4.19.2.
Overview
express is a minimalist web framework.
Affected versions of this package are vulnerable to Open Redirect due to the implementation of URL encoding using encodeurl before passing it to the location header. This can lead to unexpected evaluations of malformed URLs by common redirect allow list implementations in applications, allowing an attacker to bypass a properly implemented allow list and redirect users to malicious sites.
Remediation
Upgrade express to version 4.19.2, 5.0.0-beta.3 or higher.
References
medium severity
- Vulnerable module: express
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8Remediation: Upgrade to express@3.11.0.
Overview
express is a minimalist web framework.
Affected versions of this package do not enforce the user's browser to set a specific charset in the content-type header while displaying 400 level response messages. This could be used by remote attackers to perform a cross-site scripting attack, by using non-standard encodings like UTF-7.
Details
<
Recommendations
Update express to 3.11.0, 4.5.0 or higher.
References
medium severity
- Vulnerable module: send
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › send@0.1.4Remediation: Upgrade to express@3.19.1.
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › send@0.1.4Remediation: Upgrade to express@4.0.0.
Overview
Send is a library for streaming files from the file system as an http response. It supports partial responses (Ranges), conditional-GET negotiation, high test coverage, and granular events which may be leveraged to take appropriate actions in your application or framework.
Affected versions of this package are vulnerable to a Root Path Disclosure.
Remediation
Upgrade send to version 0.11.1 or higher.
If a direct dependency update is not possible, use snyk wizard to patch this vulnerability.
References
medium severity
- Vulnerable module: socket.io
- Introduced through: socket.io@0.9.19
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › socket.io@0.9.19Remediation: Upgrade to socket.io@2.4.0.
Overview
socket.io is a node.js realtime framework server.
Affected versions of this package are vulnerable to Insecure Defaults due to CORS Misconfiguration. All domains are whitelisted by default.
Remediation
Upgrade socket.io to version 2.4.0 or higher.
References
medium severity
- Vulnerable module: uglify-js
- Introduced through: socket.io@0.9.19
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › socket.io@0.9.19 › socket.io-client@0.9.16 › uglify-js@1.2.5Remediation: Upgrade to socket.io@1.0.1.
Overview
uglify-js is a JavaScript parser, minifier, compressor and beautifier toolkit.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the string_template and the decode_template functions.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
AThe string must start with the letter 'A'(B|C+)+The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+matches one or more times). The+at the end of this section states that we can look for one or more matches of this section.DFinally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
| String | Number of C's | Number of steps |
|---|---|---|
| ACCCX | 3 | 38 |
| ACCCCX | 4 | 71 |
| ACCCCCX | 5 | 136 |
| ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade uglify-js to version 3.14.3 or higher.
References
medium severity
- Vulnerable module: uglify-js
- Introduced through: socket.io@0.9.19
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › socket.io@0.9.19 › socket.io-client@0.9.16 › uglify-js@1.2.5Remediation: Upgrade to socket.io@1.0.1.
Overview
The parse() function in the uglify-js package prior to version 2.6.0 is vulnerable to regular expression denial of service (ReDoS) attacks when long inputs of certain patterns are processed.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
AThe string must start with the letter 'A'(B|C+)+The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+matches one or more times). The+at the end of this section states that we can look for one or more matches of this section.DFinally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
| String | Number of C's | Number of steps |
|---|---|---|
| ACCCX | 3 | 38 |
| ACCCCX | 4 | 71 |
| ACCCCCX | 5 | 136 |
| ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade to version 2.6.0 or greater.
If a direct dependency update is not possible, use snyk wizard to patch this vulnerability.
References
medium severity
- Vulnerable module: ws
- Introduced through: socket.io@0.9.19
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › socket.io@0.9.19 › socket.io-client@0.9.16 › ws@0.4.32Remediation: Upgrade to socket.io@1.0.1.
Overview
ws is a simple to use websocket client, server and console for node.js.
Affected versions of the package use the cryptographically insecure Math.random() which can produce predictable values and should not be used in security-sensitive context.
Details
Computers are deterministic machines, and as such are unable to produce true randomness. Pseudo-Random Number Generators (PRNGs) approximate randomness algorithmically, starting with a seed from which subsequent values are calculated.
There are two types of PRNGs: statistical and cryptographic. Statistical PRNGs provide useful statistical properties, but their output is highly predictable and forms an easy to reproduce numeric stream that is unsuitable for use in cases where security depends on generated values being unpredictable. Cryptographic PRNGs address this problem by generating output that is more difficult to predict. For a value to be cryptographically secure, it must be impossible or highly improbable for an attacker to distinguish between it and a truly random value. In general, if a PRNG algorithm is not advertised as being cryptographically secure, then it is probably a statistical PRNG and should not be used in security-sensitive contexts.
You can read more about node's insecure Math.random() in Mike Malone's post.
Remediation
Upgrade ws to version 1.1.2 or higher.
References
medium severity
- Vulnerable module: ws
- Introduced through: socket.io@0.9.19
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › socket.io@0.9.19 › socket.io-client@0.9.16 › ws@0.4.32Remediation: Upgrade to socket.io@1.0.1.
Overview
ws is a simple to use websocket client, server and console for node.js.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). A specially crafted value of the Sec-Websocket-Protocol header can be used to significantly slow down a ws server.
##PoC
for (const length of [1000, 2000, 4000, 8000, 16000, 32000]) {
const value = 'b' + ' '.repeat(length) + 'x';
const start = process.hrtime.bigint();
value.trim().split(/ *, */);
const end = process.hrtime.bigint();
console.log('length = %d, time = %f ns', length, end - start);
}
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
AThe string must start with the letter 'A'(B|C+)+The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+matches one or more times). The+at the end of this section states that we can look for one or more matches of this section.DFinally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
| String | Number of C's | Number of steps |
|---|---|---|
| ACCCX | 3 | 38 |
| ACCCCX | 4 | 71 |
| ACCCCCX | 5 | 136 |
| ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade ws to version 7.4.6, 6.2.2, 5.2.3 or higher.
References
medium severity
- Vulnerable module: express
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8Remediation: Upgrade to express@4.20.0.
Overview
express is a minimalist web framework.
Affected versions of this package are vulnerable to Cross-site Scripting due to improper handling of user input in the response.redirect method. An attacker can execute arbitrary code by passing malicious input to this method.
Note
To exploit this vulnerability, the following conditions are required:
The attacker should be able to control the input to
response.redirect()express must not redirect before the template appears
the browser must not complete redirection before:
the user must click on the link in the template
Remediation
Upgrade express to version 4.20.0, 5.0.0 or higher.
References
medium severity
- Vulnerable module: express
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8Remediation: Upgrade to express@4.0.0.
Overview
express is a minimalist web framework.
Affected versions of this package are vulnerable to Open Redirect via the location() method in response.js.
Notes:
Express 3 has reached End-of-Life and will not receive any updates to address this issue.
This vulnerability is achievable only when: a request path begins with double slashes
//and a relative path for redirection begins with./and is provided from user-controlled input and theLocationheader is set with that user-controlled input.
Remediation
Upgrade express to version 4.0.0 or higher.
References
medium severity
- Vulnerable module: send
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › send@0.1.4Remediation: Upgrade to express@3.16.10.
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › send@0.1.4Remediation: Upgrade to express@4.0.0.
Overview
send is a library for streaming files from the file system.
Affected versions of this package are vulnerable to Directory-Traversal attacks due to insecure comparison.
When relying on the root option to restrict file access a malicious user may escape out of the restricted directory and access files in a similarly named directory. For example, a path like /my-secret is consedered fine for the root /my.
Details
A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.
Directory Traversal vulnerabilities can be generally divided into two types:
- Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.
st is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public route.
If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.
curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa
Note %2e is the URL encoded version of . (dot).
- Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as
Zip-Slip.
One way to achieve this is by using a malicious zip archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.
The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:
2018-04-15 22:04:29 ..... 19 19 good.txt
2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys
Remediation
Upgrade to a version greater than or equal to 0.8.4.
References
low severity
- Vulnerable module: mime
- Introduced through: express@3.4.8
Detailed paths
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › send@0.1.4 › mime@1.2.11Remediation: Upgrade to express@4.16.0.
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › send@0.1.4 › mime@1.2.11Remediation: Upgrade to express@4.0.0.
Overview
mime is a comprehensive, compact MIME type module.
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). It uses regex the following regex /.*[\.\/\\]/ in its lookup, which can cause a slowdown of 2 seconds for 50k characters.
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
AThe string must start with the letter 'A'(B|C+)+The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+matches one or more times). The+at the end of this section states that we can look for one or more matches of this section.DFinally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
| String | Number of C's | Number of steps |
|---|---|---|
| ACCCX | 3 | 38 |
| ACCCCX | 4 | 71 |
| ACCCCCX | 5 | 136 |
| ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
Upgrade mime to version 1.4.1, 2.0.3 or higher.
References
low severity
- Vulnerable module: send
- Introduced through: express@3.4.8
Detailed paths
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Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › send@0.1.4Remediation: Upgrade to express@4.20.0.
-
Introduced through: hichat@wayou/hichat#c7f930042cfaf3384a4fb38bc4632e0f04eb214e › express@3.4.8 › connect@2.12.0 › send@0.1.4Remediation: Upgrade to express@4.0.0.
Overview
send is a Better streaming static file server with Range and conditional-GET support
Affected versions of this package are vulnerable to Cross-site Scripting due to improper user input sanitization passed to the SendStream.redirect() function, which executes untrusted code. An attacker can execute arbitrary code by manipulating the input parameters to this method.
Note:
Exploiting this vulnerability requires the following:
The attacker needs to control the input to
response.redirect()Express MUST NOT redirect before the template appears
The browser MUST NOT complete redirection before
The user MUST click on the link in the template
Details
Cross-site scripting (or XSS) is a code vulnerability that occurs when an attacker “injects” a malicious script into an otherwise trusted website. The injected script gets downloaded and executed by the end user’s browser when the user interacts with the compromised website.
This is done by escaping the context of the web application; the web application then delivers that data to its users along with other trusted dynamic content, without validating it. The browser unknowingly executes malicious script on the client side (through client-side languages; usually JavaScript or HTML) in order to perform actions that are otherwise typically blocked by the browser’s Same Origin Policy.
Injecting malicious code is the most prevalent manner by which XSS is exploited; for this reason, escaping characters in order to prevent this manipulation is the top method for securing code against this vulnerability.
Escaping means that the application is coded to mark key characters, and particularly key characters included in user input, to prevent those characters from being interpreted in a dangerous context. For example, in HTML, < can be coded as < and > can be coded as > in order to be interpreted and displayed as themselves in text, while within the code itself, they are used for HTML tags. If malicious content is injected into an application that escapes special characters and that malicious content uses < and > as HTML tags, those characters are nonetheless not interpreted as HTML tags by the browser if they’ve been correctly escaped in the application code and in this way the attempted attack is diverted.
The most prominent use of XSS is to steal cookies (source: OWASP HttpOnly) and hijack user sessions, but XSS exploits have been used to expose sensitive information, enable access to privileged services and functionality and deliver malware.
Types of attacks
There are a few methods by which XSS can be manipulated:
| Type | Origin | Description |
|---|---|---|
| Stored | Server | The malicious code is inserted in the application (usually as a link) by the attacker. The code is activated every time a user clicks the link. |
| Reflected | Server | The attacker delivers a malicious link externally from the vulnerable web site application to a user. When clicked, malicious code is sent to the vulnerable web site, which reflects the attack back to the user’s browser. |
| DOM-based | Client | The attacker forces the user’s browser to render a malicious page. The data in the page itself delivers the cross-site scripting data. |
| Mutated | The attacker injects code that appears safe, but is then rewritten and modified by the browser, while parsing the markup. An example is rebalancing unclosed quotation marks or even adding quotation marks to unquoted parameters. |
Affected environments
The following environments are susceptible to an XSS attack:
- Web servers
- Application servers
- Web application environments
How to prevent
This section describes the top best practices designed to specifically protect your code:
- Sanitize data input in an HTTP request before reflecting it back, ensuring all data is validated, filtered or escaped before echoing anything back to the user, such as the values of query parameters during searches.
- Convert special characters such as
?,&,/,<,>and spaces to their respective HTML or URL encoded equivalents. - Give users the option to disable client-side scripts.
- Redirect invalid requests.
- Detect simultaneous logins, including those from two separate IP addresses, and invalidate those sessions.
- Use and enforce a Content Security Policy (source: Wikipedia) to disable any features that might be manipulated for an XSS attack.
- Read the documentation for any of the libraries referenced in your code to understand which elements allow for embedded HTML.
Remediation
Upgrade send to version 0.19.0, 1.1.0 or higher.