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  4. CVE 2026 63571 attribute certificate path validation does not
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Back to active CVEs
High · CVSS 8.7CVE-2026-63571

Attribute certificate path validation does not verify the attribute certificate's signature

Answer in brief

CVE-2026-63571 records a High severity (CVSS 8.7) vulnerability in Attribute certificate path validation does not verify the attribute certificate's signature. The current sources do not mark it as known exploited. The current feed maps Legion of the Bouncy Castle Inc./BouncyCastle.Cryptography (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 2, 2026Updated Oct 2, 2026Source checked Oct 2, 2026First seen by HOL Oct 2, 2026Material review Oct 2, 2026
Upstream Advisory

Key facts

Risk
High · CVSS 8.7
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Legion of the Bouncy Castle Inc./BouncyCastle.Cryptography (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
Legion of the Bouncy Castle Inc./BouncyCastle.Cryptographygeneric>=0 <2.7.02.7.0

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for Legion of the Bouncy Castle Inc./BouncyCastle.Cryptography.
  2. 2Review the reported fix. Update Legion of the Bouncy Castle Inc./BouncyCastle.Cryptography to 2.7.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Oct 2, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 2, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Oct 2, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
Upstream source description

Improper verification of cryptographic signature in the attribute certificate path validator (PkixAttrCertPathValidator, also used by PkixAttrCertPathBuilder) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker to have a forged X.509 attribute certificate accepted as valid, and so obtain whatever roles or privileges an application grants on the strength of its attributes, via an attribute certificate that names a trusted attribute authority as its issuer but was not signed by it, because the RFC 3281 validation steps check the holder and issuer certification paths, validity period, extensions and revocation status but never verify the attribute certificate's signature with the issuer's public key. Only applications that use these classes to validate attribute certificates are affected.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

  • CcmBlockCipher and KCcmBlockCipher leave unverified plaintext in the output buffer after a failed tag checkSame legion of the bouncy castle inc./bouncycastle.cryptography package
  • Name constraints bypass via trailing dot in rfc822Name, dNSName and URI hostsSame legion of the bouncy castle inc./bouncycastle.cryptography package
  • Unbounded HSS public key level count allows huge array allocation during signature verificationSame legion of the bouncy castle inc./bouncycastle.cryptography package
  • Quadratic-time escaping when converting X.509 distinguished names to stringsSame legion of the bouncy castle inc./bouncycastle.cryptography package
  • Kubio AI Page Builder <= 2.9.2 - Unauthenticated Stored Cross-Site Scripting via SVG Comment Content (KSES Allowlist Bypass)Same generic ecosystem
  • Download Monitor <= 5.2.10 - Unauthenticated Stored Cross-Site Scripting via Cross-Origin postMessage to Admin EditorSame generic ecosystem

Record context

Vulnerability class
Vulnerability
EPSS
Not reported
CWE IDs
CWE-347
Source
CVE List V5
Source checked
Oct 2, 2026
References
2 linked sources
Open source record