ANT-2026-0HC68EK6 · libreoffice

heap-buffer-overflow medium

CVE-2026-6047

Severity Claude medium · Security research firm medium · Maintainer medium

Discovered by Claude Mythos Preview

REPORT

Anthropic's analysis, sealed at approval. Disclosure to the maintainer was performed by Ada Logics.

ANT-2026-0HC68EK6: Heap Buffer Overflow via Unsafe static_cast in OOXML VML Textbox Replay

An unsafe static_cast during OOXML VML textbox replay leads to a heap buffer overflow.

Target

Project: libreoffice
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-2026-0HC68EK6.

Reference: ANT-2026-0HC68EK6
Anthropic CVD Policy: https://www.anthropic.com/coordinated-vulnerability-disclosure

SECURITY RESEARCH FIRM ANALYSIS

Triage and disclosure were performed by Ada Logics.

Verdict
true positive
Severity
medium
TIMELINE

Dates from discovery through public reveal.

  1. 2026-03-29 Reported to tracker
  2. 2026-04-09 Sent to maintainer
  3. 2026-05-09 Maintainer acknowledged
  4. 2026-06-14 Patch released
  5. 2026-08-17 Publicly revealed
PROVENANCE

SHA-3-512 hash:

e9bf4f825b88579f81f949386ec89f4f57327bfa9240c6784aff1cf24ac4555dfa9cab15854b2ef17675c8be0d305ada2d0c3cfd3b6100cbc6f374c9030bb70e

Committed 2026-04-09 11:50 PT

Revealed 2026-08-17 10:47 PT

Verify (download preimage.json)

Show preimage JSON 
{
  "ant_id": "ANT-2026-0HC68EK6",
  "bug_class": "Heap Buffer Overflow",
  "claude_severity": "medium",
  "commit_sha": null,
  "created_at": "2026-03-29T20:43:11+00:00",
  "description": "An unsafe static_cast during OOXML VML textbox replay leads to a heap buffer overflow.",
  "discovered_at": null,
  "location": null,
  "poc_sha256": null,
  "preimage_version": 1,
  "project": "LibreOffice",
  "reproduction": null,
  "technical_details": null,
  "title": "Heap Buffer Overflow via Unsafe static_cast in OOXML VML Textbox Replay",
  "vendor_severity": "medium"
}