CVE-2026-103602: legion of the bouncy castle inc. bc-csharp Improper Certificate Validation

Vulnerability summary

CVE-2026-103602 is a high (CVSS 8.2) Improper Certificate Validation vulnerability in legion of the bouncy castle inc. bc-csharp. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 14.6% of scored vulnerabilities.

Timeline

1. 02-10-2026
   PublishedVulnerability first disclosed.
2. 02-10-2026
   Last modifiedVulnerability information updated.

Description

Improper certificate validation in PkixNameConstraintValidator in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who controls, or can obtain certificates from, a name-constrained intermediate CA to have certificates accepted during PKIX certification path validation for email addresses, DNS names or URI hosts that lie within excluded subtrees applying to that CA, via an rfc822Name, dNSName or uniformResourceIdentifier name whose host ends with a dot, because names and constraints were compared without first removing the RFC 1034 root-label trailing dot, so a fully qualified host name did not match an excluded subtree for the same host written without the dot.

• CWE-295Improper Certificate ValidationThe product does not validate, or incorrectly validates, a certificate.