Packages

ModerateVulnerabilityGHSA-968p-4wvh-cqc8CVE-2025-27789Published 11 Mar 2025

Babel has inefficient RegExp complexity in generated code with .replace when transpiling named capturing groups

Affected releases · @babel/helpers

  • 7.x7.0.0 – 7.26.9Fixed in 7.26.10

On 7.x, the newest line:

npm install @babel/helpers@7.26.10
8.x

  1. Not affected

    8.0.0 – 8.0.7

    3 releases, latest

7.x

  1. Affected

    7.0.0 – 7.26.9

    98 releases

  2. Fixed

    7.26.10 – 7.29.10

    13 releases

114 stable releases of @babel/helpers, oldest to newest, one row per major.

Affected releases · @babel/runtime

  • 7.x7.0.0 – 7.26.9Fixed in 7.26.10

On 7.x, the newest line:

npm install @babel/runtime@7.26.10
8.x

  1. Not affected

    8.0.0 – 8.0.7

    3 releases, latest

7.x

  1. Affected

    7.0.0 – 7.26.9

    123 releases

  2. Fixed

    7.26.10 – 7.29.10

    13 releases

139 stable releases of @babel/runtime, oldest to newest, one row per major.

Is your project affected?

Paste your package.json, or type the range you declare for @babel/helpers. It is read in your browser and sent nowhere.

Is your project affected?

Paste your package.json, or type the range you declare for @babel/runtime. It is read in your browser and sent nowhere.

What happens

Impact

When using Babel to compile regular expression named capturing groups, Babel will generate a polyfill for the .replace method that has quadratic complexity on some specific replacement pattern strings (i.e. the second argument passed to .replace).

Your generated code is vulnerable if all the following conditions are true:

  • You use Babel to compile regular expression named capturing groups

  • You use the .replace method on a regular expression that contains named capturing groups

  • Your code uses untrusted strings as the second argument of .replace

If you are using @babel/preset-env with the targets option, the transform that injects the vulnerable code is automatically enabled if:

  • you use duplicated named capturing groups, and target any browser older than Chrome/Edge 126, Opera 112, Firefox 129, Safari 17.4, or Node.js 23

  • you use any named capturing groups, and target any browser older than Chrome 64, Opera 71, Edge 79, Firefox 78, Safari 11.1, or Node.js 10

You can verify what transforms @babel/preset-env is using by enabling the debug option.

Patches

This problem has been fixed in @babel/helpers and @babel/runtime 7.26.10 and 8.0.0-alpha.17, please upgrade. It's likely that you do not directly depend on @babel/helpers, and instead you depend on @babel/core (which itself depends on @babel/helpers). Upgrading to @babel/core 7.26.10 is not required, but it guarantees that you are on a new enough @babel/helpers version.

Please note that just updating your Babel dependencies is not enough: you will also need to re-compile your code.

Workarounds

If you are passing user-provided strings as the second argument of .replace on regular expressions that contain named capturing groups, validate the input and make sure it does not contain the substring $< if it's then not followed by > (possibly with other characters in between).

References

This vulnerability was reported and fixed in #17173.