Bug 2453205 (CVE-2026-32884)

Summary: CVE-2026-32884 Botan: Botan: Certificate validation bypass due to mixed-case Common Name in X.509 certificates
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Botan, a C++ cryptography library. During the processing of X.509 certificate paths with DNS name constraints, the library incorrectly handles mixed-case Common Names (CN) in end-entity certificates that lack a Subject Alternative Name. A remote attacker could exploit this by crafting a malicious certificate with a mixed-case CN to bypass `excludedSubtrees` constraints. This vulnerability could lead to a certificate validation bypass, allowing an attacker to present a certificate that should have been rejected.
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Bug Depends On: 2453758, 2453760, 2453756, 2453757, 2453759, 2453761    
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Description OSIDB Bzimport 2026-03-30 21:02:31 UTC 
Botan is a C++ cryptography library. Prior to version 3.11.0, during processing of an X.509 certificate path using name constraints which restrict the set of allowable DNS names, if no subject alternative name is defined in the end-entity certificate Botan would check that the CN was allowed by the DNS name constraints, even though this check is technically not required by RFC 5280. However this check failed to account for the possibility of a mixed-case CN. Thus a certificate with CN=Sub.EVIL.COM and no subject alternative name would bypasses an excludedSubtrees constraint for evil.com because the comparison is case-sensitive. This issue has been patched in version 3.11.0.