Summary
ReDOS vulnerabities: multiple grammars
Impact: Potential ReDOS vulnerabilities (exponential and polynomial RegEx backtracking)
The Regular expression Denial of Service (ReDoS) is a Denial of Service attack, that exploits the fact that most Regular Expression implementations may reach extreme situations that cause them to work very slowly (exponentially related to input size). An attacker can then cause a program using a Regular Expression to enter these extreme situations and then hang for a very long time.
If are you are using Highlight.js to highlight user-provided data you are possibly vulnerable. On the client-side (in a browser or Electron environment) risks could include lengthy freezes or crashes... On the server-side infinite freezes could occur... effectively preventing users from accessing your app or service (ie, Denial of Service).
This is an issue with grammars shipped with the parser (and potentially 3rd party grammars also), not the parser itself. If you are using Highlight.js with any of the following grammars you are vulnerable. If you are using highlightAuto to detect the language (and have any of these grammars registered) you are vulnerable. Exponential grammars (C, Perl, JavaScript) are auto-registered when using the common grammar subset/library require('highlight.js/lib/common') as of 10.4.0 - see https://cdn.jsdelivr.net/gh/highlightjs/[email protected]/build/highlight.js
All versions prior to 10.4.1 are vulnerable, including version 9.18.5.
Grammars with exponential backtracking issues:
- c-like (c, cpp, arduino)
- handlebars (htmlbars)
- gams
- perl
- jboss-cli
- r
- erlang-repl
- powershell
- routeros
- livescript (10.4.0 and 9.18.5 included this fix)
- javascript & typescript (10.4.0 included partial fixes)
And of course any aliases of those languages have the same issue. ie: hpp is no safer than cpp.
Grammars with polynomial backtracking issues:
- kotlin
- gcode
- d
- aspectj
- moonscript
- coffeescript/livescript
- csharp
- scilab
- crystal
- elixir
- basic
- ebnf
- ruby
- fortran/irpf90
- livecodeserver
- yaml
- x86asm
- dsconfig
- markdown
- ruleslanguage
- xquery
- sqf
And again: any aliases of those languages have the same issue. ie: ruby and rb share the same ruby issues.
Workarounds / Mitigations
- Discontinue use the affected grammars. (or perhaps use only those with poly vs exponential issues)
- Attempt cherry-picking the grammar fixes into older versions...
- Attempt using newer CDN versions of any affected languages. (ie using an older CDN version of the library with newer CDN grammars). Your mileage may vary.
References
For more information
If you have any questions or comments about this advisory:
- Open an issue: https://github.com/highlightjs/highlight.js/issues
- Email us at [email protected]
Impact
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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- Version 10.4.1 resolves these vulnerabilities. Please upgrade.
Frequently Asked Questions
- What is GHSA-7WWV-VH3V-89CQ? GHSA-7WWV-VH3V-89CQ is a medium-severity improper input validation vulnerability in highlight.js (npm), affecting versions >= 9.0.0, < 10.4.1. It is fixed in 10.4.1. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- Which packages are affected by GHSA-7WWV-VH3V-89CQ?
highlight.js(npm) (versions >= 9.0.0, < 10.4.1)@highlightjs/cdn-assets(npm) (versions < 10.4.1)
- Is there a fix for GHSA-7WWV-VH3V-89CQ? Yes. GHSA-7WWV-VH3V-89CQ is fixed in 10.4.1. Upgrade to this version or later.
- Is GHSA-7WWV-VH3V-89CQ exploitable, and should I be worried? Whether GHSA-7WWV-VH3V-89CQ is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-7WWV-VH3V-89CQ is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-7WWV-VH3V-89CQ?
- Upgrade
highlight.jsto 10.4.1 or later - Upgrade
@highlightjs/cdn-assetsto 10.4.1 or later
- Upgrade