CVE-2026-63576

Improper certificate validation in PkixNameConstraintValidator (ExtractHostFromURL) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a name-constrained subordinate CA, or anyone able to obtain certificates with chosen subjectAltName URIs from such a CA, to bypass permitted or excluded uniformResourceIdentifier name constraints during certification path validation via a URI whose path, query, fragment or userinfo contains characters such as '@' or ':', because the host was extracted by string slicing without first isolating the RFC 3986 authority component, so the host compared against the constraints could differ from the URI's actual host.

Score

CVSS 4.0 8.2 High

Status

Analyzed - 91579145-5d7b-4cc5-b925-a0262ff19630

Published

2026-10-02

Last modified

2026-10-28

Weaknesses

CWE-295

Affected products

• Bc-csharp (Bouncycastle)
• Bc-csharp (Legion Of The Bouncy Castle Inc.)

References

• https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63576
• https://github.com/bcgit/bc-csharp/commit/f196a22bbf7765cc19b0c4f4645c74ea7ad35e09