Vulnerability · Published Oct 28, 2026 · Assigned by GitHub_M

CVE-2026-116795RE2JS: Quadratic-time denial of service in re2js lookbehind matching

High 7.5

In plain English

A high-severity regular-expression denial of service in re2js from le0pard. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.5%top 59.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

RE2JS is the JavaScript port of RE2, a regular expression engine that provides linear time matching. From 2.2.0 until 2.8.7, enabling LOOKBEHINDS and using repeated matching through matcher().find(), matchAll(), split(), or matcher().replaceAll() can cause quadratic total work. Machine.match restarts lookbehind scanning from offset zero for each requested start position, while Matcher-based APIs request capture slots that prevent the early exit used for captureless matching. Dense matches therefore repeatedly rescan the input, allowing attacker-influenced text to monopolize a single-threaded worker and deny service. This issue is fixed in version 2.8.7.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	re2js	2.8.7	GHSA-gg6h-894w-4m9c

Affected products (as reported)

Vendor	Product	Versions
le0pard	re2js	>= 2.2.0, < 2.8.7

Weakness: CWE-407, CWE-1333 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/le0pard/re2js/security/advisories/GHSA-gg6h-894w-4m9c x_refsource_CONFIRM
https://github.com/le0pard/re2js/pull/59 x_refsource_MISC
https://github.com/le0pard/re2js/commit/dfdd947785dfa113bdc97416375c246a39458395 x_refsource_MISC
https://github.com/le0pard/re2js/releases/tag/2.8.7 x_refsource_MISC