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ReDOS vulnerabities: multiple grammarsGHSA-7wwv-vh3v-89cq

Fix: highlightjs/highlight.js@373b9d8

GHSA-7wwv-vh3v-89cq is a security vulnerability in highlight.js. A fix is available for highlight.js — see the affected versions and patch details below.

Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Sep 10, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

8Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream
highlight.jsnpm
38.1Mdownloads / week
@highlightjs/cdn-assetsnpm
64Kdownloads / week

Description

Impact: Potential ReDOS vulnerabilities (exponential and polynomial RegEx backtracking)

oswasp:

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.

Patches

  • Version 10.4.1 resolves these vulnerabilities. Please upgrade.

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:

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
📦npmhighlight.js≥ 9.0.0&&< 10.4.110.4.1npm install highlight.js@10.4.1
📦npm@highlightjs/cdn-assetsall versions10.4.1npm install @highlightjs/cdn-assets@10.4.1

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for highlight.js, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update highlight.js to 10.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-7wwv-vh3v-89cq is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

### Impact: Potential ReDOS vulnerabilities (exponential and polynomial RegEx backtracking) [oswasp](https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS): > 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
O3 Security · Impact-Aware SCA

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ReDOS vulnerabities: multiple grammars