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Fencer Intel
medium 6.2

CVE-2025-27789 json

Inefficient RexExp complexity in generated code with .replace when transpiling named capturing groups

published last yr. modified last mo. also EUVD-2025-7806 , GHSA-968p-4wvh-cqc8

cvss
6.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 47%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm @babel/helpers 7.26.10, 8.0.0-alpha.17
  • npm @babel/runtime 7.26.10, 8.0.0-alpha.17
  • npm @babel/runtime-corejs2 7.26.10, 8.0.0-alpha.17
  • npm @babel/runtime-corejs3 7.26.10, 8.0.0-alpha.17
  • babel babel 7.26.10, 8.0.0-alpha.17
  • babeljs babel 7.26.10, 8.0.0-alpha.17

Is CVE-2025-27789 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
last yr.

Exploit prediction

0.56% chance of exploitation in the next 30 days, higher than 47% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 6.2 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 6.2 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
npm @babel/helpers
<7.26.10
>=8.0.0-alpha.0, <8.0.0-alpha.17
7.26.10
8.0.0-alpha.17
npm @babel/runtime
<7.26.10
>=8.0.0-alpha.0, <8.0.0-alpha.17
7.26.10
8.0.0-alpha.17
npm @babel/runtime-corejs2
<7.26.10
>=8.0.0-alpha.0, <8.0.0-alpha.17
7.26.10
8.0.0-alpha.17
npm @babel/runtime-corejs3
<7.26.10
>=8.0.0-alpha.0, <8.0.0-alpha.17
7.26.10
8.0.0-alpha.17

Affected products

  • babel babel

Classification

Weakness
  • CWE-1333 Inefficient Regular Expression Complexity

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.