ANT-2026-PJV7Z0AR · open62541

integer-overflow high

CVE-2026-63559 CVE-2026-65423

Severity Claude high · Security research firm high · Maintainer high

Discovered by Claude Mythos Preview

REPORT

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

ANT-2026-PJV7Z0AR: Integer overflow in variant dimension validation allowing wild-address write via arrayDimensions product overflow

The product of arrayDimensions overflows during variant dimension validation, leading to a wild-address write.

Target

Project: open62541
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-PJV7Z0AR.

Reference: ANT-2026-PJV7Z0AR
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
high
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. 2026-07-22 Patch released
  5. 2026-08-17 Publicly revealed
PROVENANCE

SHA-3-512 hash:

03bf968a7d024ab0ac6f945f14f827bdfa8fba50c910ca06cf6b2af74116597317a198657ed216efa65014c755f20e9ed5a8e2c162b139e74b5c054f55f3e198

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-PJV7Z0AR",
  "bug_class": "Integer Overflow",
  "claude_severity": "high",
  "commit_sha": null,
  "created_at": "2026-03-29T20:43:19+00:00",
  "description": "The product of arrayDimensions overflows during variant dimension validation, leading to a wild-address write.",
  "discovered_at": null,
  "location": null,
  "poc_sha256": null,
  "preimage_version": 1,
  "project": "open62541",
  "reproduction": null,
  "technical_details": null,
  "title": "Integer overflow in variant dimension validation allowing wild-address write via arrayDimensions product overflow",
  "vendor_severity": "high"
}