re2: Out-of-bounds heap read in exec/test/match via attacker-influenced lastIndex on a non-ASCII subject → uncatchable process crash (DoS)

Exploitation

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

CVSS

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

EPSS

• CVE-2026-67550: 0.16% estimated exploitation activity in the next 30 days; percentile 5.33 (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.

Summary re2 validates the user-settable lastIndex against the subject's UTF-8 byte length but then uses it as a UTF-16 code-unit count to walk the subject buffer, with no bounds check. For any non-ASCII subject, the byte length is larger than the true character count, so a lastIndex between those two values passes validation while pointing past the end of the buffer. The subsequent walk reads out of bounds. With a large subject the read marches into unmapped memory and the process dies with SIGABRT/SIGSEGV — an uncatchable crash (try/catch cannot stop it), i.e. a denial of service for any worker/process that runs the match. In some cases the out-of-bounds bytes are copied into the returned value (a bounded, best-effort heap information leak). Root cause The subject wrapper stores the UTF-8 byte length in StrVal::length: - lib/addon.cc:200 auto argLength = utf8Length(s, isolate); — UTF-8 byte count - lib/addon.cc:209 lastStringValue.reset(buffer, argSize, argLength, startFrom, false,…

Published by the source

31 Jul 2026, 16:53 UTC

Last modified by the source

31 Jul 2026, 16:53 UTC

Source last checked

26 Oct 2026, 13:00 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-ff84-5f28-78qj

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# Patch Next advisory brief: CVE-2026-67550

Advisory: re2: Out-of-bounds heap read in `exec`/`test`/`match` via attacker-influenced `lastIndex` on a non-ASCII subject → uncatchable process crash (DoS)
IDs: CVE-2026-67550, GHSA-ff84-5f28-78qj
Record: https://patchnext.com/advisories/cve-2026-67550 (revision 1, source checked 26 Oct 2026, 13:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: re2 1.25.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm re2: affected <= 1.25.1; fixed in 1.25.2

## Suggested inspection (read-only)
- `npm ls re2 --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 re2.
- 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://github.com/advisories/GHSA-ff84-5f28-78qj (GitHub-reviewed advisory GHSA-ff84-5f28-78qj lists affected ranges: npm re2 >=0 <=1.25.1)

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