TI-2026-65846 Aliases CVE-2026-63571 GHSA-cwfr-988g-hf77

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

MEDIUM 43CWE-347Published 2026-10-02 · Updated 2026-10-02

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Security bypass
Confidentiality · integrity · availability: None · High · None
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-347.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.0014 3rd percentileScored 2026-11-07

Fix Fixed bc-csharp (Legion of the Bouncy Castle Inc.): 2.7.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Legion of the Bouncy Castle Inc.	bc-csharp	before 2.7.0	2.7.0	Patch available	CNA

bc-csharp VendorLegion of the Bouncy Castle Inc. Affected before 2.7.0 Fixed in 2.7.0 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:bouncycastle:bc-csharp::::::::	before 2.7.0	Vulnerable	Legion of the Bouncy Castle Inc.

cpe:2.3:a:bouncycastle:bc-csharp:*:*:*:*:*:*:*:* Versions before 2.7.0 Vulnerable ·Legion of the Bouncy Castle Inc.

Remediation

Fix · CNA bc-csharp (Legion of the Bouncy Castle Inc.) Fixed in 2.7.0

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

Release · 2026-10-02
Legion of the Bouncy Castle bc-csharp 2.7.0
21 records Highest priority Priority MEDIUM 8 MEDIUM, 13 LOW
Other records, highest priority first
- TI-2026-65844 MTI/A0 DHAgreement does not validate the peer's ephemeral valuePriority MEDIUM 47
- TI-2026-66020 Unbounded HSS public key level count allows huge array allocation during signature verificationPriority MEDIUM 44
- TI-2026-66017 Unbounded ASN.1 nesting depth causes process-terminating stack overflowPriority MEDIUM 44
Show all 21 records →

Timeline

2026-10-02 Threatist record created from CVE-2026-63571
2026-10-03 Alias added: GHSA-cwfr-988g-hf77
2026-10-28 CVSS score added · NVD

References

Patch 2

TI-2026-65844 MTI/A0 DHAgreement does not validate the peer's ephemeral value CVSS 4.0CRITICAL 9.1
TI-2026-66020 Unbounded HSS public key level count allows huge array allocation during signature verification CVSS 4.0HIGH 8.7
TI-2026-66017 Unbounded ASN.1 nesting depth causes process-terminating stack overflow CVSS 4.0HIGH 8.7
TI-2026-65849 Unbounded allocation from OpenPGP signature and user attribute subpacket lengths CVSS 4.0HIGH 8.7
TI-2026-65843 Unbounded CMP/CRMF password-based MAC iteration count allows CPU exhaustion CVSS 4.0HIGH 8.7
TI-2026-65841 DTLS handshake reassembler allocates buffer from unchecked 24-bit length CVSS 4.0HIGH 8.7

See all 21 →

Sources

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