Go crypto/x509 excluded subdomain constraint wildcard SAN bypass
CVE-2025-61727 is a certificate name-constraints enforcement flaw in Go's crypto/x509 certificate validation logic. According to the provided content, an excluded subdomain constraint in a certificate chain does not properly restrict wildcard Subject Alternative Names (SANs) asserted by the leaf certificate. For example, if a CA-imposed name constraint excludes the subdomain test.example.com, a leaf certificate can still claim a wildcard SAN such as *.example.com and be accepted when it should be rejected under the excluded-subtree policy. This results in improper enforcement of X.509 DNS name constraints during certificate chain validation.
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