ANT-2026-RVPC18B1 · libgit2/libgit2

heap-buffer-overflow medium

Severity Claude medium · Security research firm medium · Maintainer -

Discovered by Claude Mythos Preview

REPORT

Anthropic's analysis, sealed at approval. Disclosure to the maintainer was performed by Trail of Bits.

ANT-2026-RVPC18B1: Heap buffer overflow in bundled PCRE regex compilation via pre-compile/compile phase mismatch in atomic wrapping

A size mismatch between PCRE's pre-compile and compile phases when applying atomic-group wrapping leads to a heap buffer overflow during regex compilation.

Target

Project: libgit2
Discovery: static analysis — not yet dynamically reproduced

Reproduction

This finding was identified by static analysis and has not yet been dynamically reproduced. A trigger input is not included.

[No reproducer or sanitizer output attached — request from security-cvd@anthropic.com if needed.]

Acknowledgement

This vulnerability was discovered by Claude, Anthropic's AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research. Please direct questions to security-cvd@anthropic.com and reference ANT-2026-RVPC18B1.

Reference: ANT-2026-RVPC18B1
Anthropic CVD Policy: https://www.anthropic.com/coordinated-vulnerability-disclosure

SECURITY RESEARCH FIRM ANALYSIS

Triage and disclosure were performed by Trail of Bits.

Verdict: true positive
Severity: medium

TIMELINE

Dates from discovery through public reveal.

2026-03-29 Reported to tracker
2026-04-09 Sent to maintainer
2026-05-09 Maintainer acknowledged
2026-05-31 Patch released
2026-08-17 Publicly revealed

PROVENANCE

SHA-3-512 hash:

ff61b166630b666ba65794e93dc603c73b94d689cb24e5e278ccc9aaec77357155e8ed59e4a584226659042238d5105aba3cf083f1409261b11d5495faed05b2

Committed 2026-04-09 11:49 PT

Revealed 2026-08-17 10:47 PT

Verify (download preimage.json)

Show preimage JSON

{
  "ant_id": "ANT-2026-RVPC18B1",
  "bug_class": "Heap Buffer Overflow",
  "claude_severity": "medium",
  "commit_sha": null,
  "created_at": "2026-03-29T20:43:06+00:00",
  "description": "A size mismatch between PCRE's pre-compile and compile phases when applying atomic-group wrapping leads to a heap buffer overflow during regex compilation.",
  "discovered_at": null,
  "location": null,
  "poc_sha256": null,
  "preimage_version": 1,
  "project": "libgit2",
  "reproduction": null,
  "technical_details": null,
  "title": "Heap buffer overflow in bundled PCRE regex compilation via pre-compile/compile phase mismatch in atomic wrapping",
  "vendor_severity": "medium"
}