Bug 2568538 (CVE-2026-48057)

Summary: CVE-2026-48057 botan: botan: Name constraint bypass via multi-valued RDN certificate parsing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Botan. When parsing X.509 digital certificates, the Distinguished Name decoder mishandles multi-valued Relative Distinguished Names (RDNs), leading to a name constraint bypass. An attacker controlling a restricted intermediate Certificate Authority (CA) can exploit this flaw by issuing a certificate that pairs a permitted name with an unauthorized name. This allows the attacker to circumvent domain restrictions and impersonate unauthorized hostnames in environments that do not use Subject Alternative Names (SANs).
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Description OSIDB Bzimport 2026-11-06 21:31:48 UTC 
Botan is a C++ cryptography library. Prior to 3.13.0, Botan's X.509 Distinguished Name decoder flattens the Attribute-Value Assertions in each Relative Distinguished Name and loses multi-value RDN grouping before DN name-constraint enforcement. An attacker controlling a name-constrained intermediate CA can issue a certificate with a multi-value RDN whose first Common Name matches the permitted constraint and whose second Common Name is attacker-chosen, causing the constraint check to accept the flattened first value. If the certificate contains no subjectAlternativeName extension, the second Common Name can then be accepted as a hostname; Botan does not fall back to Common Name hostname matching when any subjectAlternativeName is present. The exposure is limited to deployments using DN name constraints, which are uncommon outside internal PKIs, and to certificates without a subjectAlternativeName. This issue is fixed in version 3.13.0.