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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.2 · CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2025-27789: 0.56% estimated exploitation activity in the next 30 days; percentile 46.87 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

11 Mar 2025, 20:30 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

24 Oct 2026, 04:13 UTC

1. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-968p-4wvh-cqc8

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# Patch Next advisory brief: CVE-2025-27789

Advisory: Babel has inefficient RegExp complexity in generated code with .replace when transpiling named capturing groups
IDs: CVE-2025-27789, GHSA-968p-4wvh-cqc8
Record: https://patchnext.com/advisories/cve-2025-27789 (revision 1, source checked 24 Oct 2026, 04:13 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @babel/runtime-corejs3 8.0.0-alpha.17, 7.26.10; @babel/helpers 8.0.0-alpha.17, 7.26.10; @babel/runtime-corejs2 8.0.0-alpha.17, 7.26.10; @babel/runtime 8.0.0-alpha.17, 7.26.10. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @babel/runtime-corejs3: affected < 7.26.10; >= 8.0.0-alpha.0, < 8.0.0-alpha.17; fixed in 7.26.10, 8.0.0-alpha.17
- npm @babel/helpers: affected < 7.26.10; >= 8.0.0-alpha.0, < 8.0.0-alpha.17; fixed in 7.26.10, 8.0.0-alpha.17
- npm @babel/runtime-corejs2: affected < 7.26.10; >= 8.0.0-alpha.0, < 8.0.0-alpha.17; fixed in 7.26.10, 8.0.0-alpha.17
- npm @babel/runtime: affected < 7.26.10; >= 8.0.0-alpha.0, < 8.0.0-alpha.17; fixed in 7.26.10, 8.0.0-alpha.17

## Suggested inspection (read-only)
- `npm ls @babel/runtime-corejs3 --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @babel/helpers --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @babel/runtime-corejs2 --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @babel/runtime --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @babel/runtime-corejs3, @babel/helpers, @babel/runtime-corejs2, @babel/runtime.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-968p-4wvh-cqc8 (OSV record GHSA-968p-4wvh-cqc8 lists affected ranges: npm @babel/helpers >=0 =8.0.0-alpha.0 =0 =8.0.0-alpha.0 =0 =8.0.0-alpha.0 =0 =8.0.0-alpha.0 <8.0.0-alpha.17 (fixed))

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