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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/bcgit/bc-csharp/commit/f196a22bbf7765cc19b0c4f4645c74ea7ad35e09	Patch
https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63576	Patch Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:bouncycastle:bc-csharp:*:*:*:*:*:*:*:*

History

28 Oct 2026, 14:38

Type	Values Removed	Values Added
CPE		cpe:2.3:a:bouncycastle:bc-csharp::::::::
References	~~() https://github.com/bcgit/bc-csharp/commit/f196a22bbf7765cc19b0c4f4645c74ea7ad35e09 -~~	() https://github.com/bcgit/bc-csharp/commit/f196a22bbf7765cc19b0c4f4645c74ea7ad35e09 - Patch
References	~~() https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63576 -~~	() https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63576 - Patch, Vendor Advisory
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 7.5
First Time		Bouncycastle bc-csharp Bouncycastle

02 Oct 2026, 08:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-02 08:17

Updated : 2026-10-28 14:38

NVD link : CVE-2026-63576

Mitre link : CVE-2026-63576

CVE.ORG link : CVE-2026-63576

JSON object : View

Products Affected

bouncycastle

bc-csharp

CWE

CWE-295

Improper Certificate Validation

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