Vulnerability · Published Oct 2, 2026 · Assigned by bcorg
CVE-2026-103602Name constraints bypass via trailing dot in rfc822Name, dNSName and URI hosts
High 8.2
In plain English
A high-severity improper certificate validation in bc-csharp from Legion of the Bouncy Castle Inc.. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 14% of all known vulnerabilities).
Official 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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Legion of the Bouncy Castle Inc. | bc-csharp | 0 – before 2.7.0 |
Weakness: CWE-295 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
References
- https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103602 vendor-advisory
- https://github.com/bcgit/bc-csharp/commit/f196a22bbf7765cc19b0c4f4645c74ea7ad35e09 patch
- https://github.com/bcgit/bc-csharp/commit/be276e057775a6a674a62e9d9a2583b229978f73 patch
- https://github.com/bcgit/bc-csharp/commit/75c3c576602886180ed92a63c89419e3bd63b392 patch