alfred-ldoce@1.1.2

Vulnerabilities

5 via 12 paths

Dependencies

233

Source

npm

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Severity
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critical severity

Sandbox Escaping

  • Vulnerable module: safe-eval
  • Introduced through: google-translate-api@2.3.0

Detailed paths

  • Introduced through: alfred-ldoce@1.1.2 google-translate-api@2.3.0 safe-eval@0.3.0

Overview

[safe-eval] is a version of eval, claiming to be safer.

Affected versions of this package are vulnerable to Sandbox Escaping. User input is not sanitized before being passed on to the safeEval function. A malicious user could access the object constructors, allowing access to the standard library, then escaping the sandbox.

Proof of Concept:

var safeEval = require('safe-eval');
safeEval("this.constructor.constructor('return process')().exit()");

Remediation

Upgrade safe-eval to version 0.4.0 or higher.

References

high severity

Regular Expression Denial of Service (ReDoS)

  • Vulnerable module: plist
  • Introduced through: alfred-notifier@0.2.3 and alfy@0.6.0

Detailed paths

  • Introduced through: alfred-ldoce@1.1.2 alfred-notifier@0.2.3 plist@2.1.0
  • Introduced through: alfred-ldoce@1.1.2 alfy@0.6.0 alfred-notifier@0.2.3 plist@2.1.0
  • Introduced through: alfred-ldoce@1.1.2 alfy@0.6.0 alfred-link@0.2.1 plist@2.1.0

Overview

plist is a Mac OS X Plist parser/builder for Node.js and browsers

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) attacks due to bundling a vulnerable version of the XMLBuilder package. This can cause an impact of about 10 seconds matching time for data 60 characters long.

Disclosure Timeline

  • Feb 5th, 2018 - Initial Disclosure to package owner
  • Feb 6th, 2018 - Initial Response from package owner
  • Mar 18th, 2018 - Fix issued
  • Apr 15th, 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.

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 plist to version 3.0.1 or higher.

References

high severity

Sandbox Escape

  • Vulnerable module: safe-eval
  • Introduced through: google-translate-api@2.3.0

Detailed paths

  • Introduced through: alfred-ldoce@1.1.2 google-translate-api@2.3.0 safe-eval@0.3.0

Overview

safe-eval is a Safer version of eval()

Affected versions of this package are vulnerable to Sandbox Escape. It is possible for an attacker to run an arbitrary command on the host machine.

POC by Anirudh Anand (for node 12.13.0)

const safeEval = require('safe-eval');

const theFunction = function() {
   const bad = new Error();
   bad.__proto__ = null;
   bad.stack = {
      match(outer) {
         throw outer.constructor.constructor("return process")().mainModule.require('child_process').execSync('whoami').toString();
      }
   };
   return bad;
};

const untrusted = `(${theFunction})()`;
console.log(safeEval(untrusted));

Remediation

There is no fixed version for safe-eval.

References

medium severity

Prototype Pollution

  • Vulnerable module: dot-prop
  • Introduced through: alfy@0.6.0 and google-translate-api@2.3.0

Detailed paths

  • Introduced through: alfred-ldoce@1.1.2 alfy@0.6.0 conf@0.11.2 dot-prop@3.0.0
    Remediation: Upgrade to alfred-ldoce@1.2.0.
  • Introduced through: alfred-ldoce@1.1.2 google-translate-api@2.3.0 configstore@2.1.0 dot-prop@3.0.0
  • Introduced through: alfred-ldoce@1.1.2 alfy@0.6.0 cache-conf@0.3.0 conf@0.11.2 dot-prop@3.0.0
    Remediation: Upgrade to alfred-ldoce@1.2.0.
  • Introduced through: alfred-ldoce@1.1.2 google-translate-api@2.3.0 google-translate-token@1.0.0 configstore@2.1.0 dot-prop@3.0.0

Overview

dot-prop is a package to get, set, or delete a property from a nested object using a dot path.

Affected versions of this package are vulnerable to Prototype Pollution. It is possible for a user to modify the prototype of a base object.

PoC by aaron_costello

var dotProp = require("dot-prop")
const object = {};
console.log("Before " + object.b); //Undefined
dotProp.set(object, '__proto__.b', true);
console.log("After " + {}.b); //true

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.

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 dot-prop to version 4.2.1, 5.1.1 or higher.

References

medium severity

XML External Entity (XXE) Injection

  • Vulnerable module: xmldom
  • Introduced through: alfred-notifier@0.2.3 and alfy@0.6.0

Detailed paths

  • Introduced through: alfred-ldoce@1.1.2 alfred-notifier@0.2.3 plist@2.1.0 xmldom@0.1.31
  • Introduced through: alfred-ldoce@1.1.2 alfy@0.6.0 alfred-notifier@0.2.3 plist@2.1.0 xmldom@0.1.31
  • Introduced through: alfred-ldoce@1.1.2 alfy@0.6.0 alfred-link@0.2.1 plist@2.1.0 xmldom@0.1.31

Overview

xmldom is an A pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module.

Affected versions of this package are vulnerable to XML External Entity (XXE) Injection. Does not correctly preserve system identifiers, FPIs or namespaces when repeatedly parsing and serializing maliciously crafted documents.

Details

XXE Injection is a type of attack against an application that parses XML input. XML is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. By default, many XML processors allow specification of an external entity, a URI that is dereferenced and evaluated during XML processing. When an XML document is being parsed, the parser can make a request and include the content at the specified URI inside of the XML document.

Attacks can include disclosing local files, which may contain sensitive data such as passwords or private user data, using file: schemes or relative paths in the system identifier.

For example, below is a sample XML document, containing an XML element- username.

<?xml version="1.0" encoding="ISO-8859-1"?>
   <username>John</username>
</xml>

An external XML entity - xxe, is defined using a system identifier and present within a DOCTYPE header. These entities can access local or remote content. For example the below code contains an external XML entity that would fetch the content of /etc/passwd and display it to the user rendered by username.

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE foo [
   <!ENTITY xxe SYSTEM "file:///etc/passwd" >]>
   <username>&xxe;</username>
</xml>

Other XXE Injection attacks can access local resources that may not stop returning data, possibly impacting application availability and leading to Denial of Service.

Remediation

Upgrade xmldom to version 0.5.0 or higher.

References