Certificate validation vulnerabilities

Validating certificate chains which use policies is unexpectedly inefficient when certificates in the chain contain a very large number of policy mappings, possibly causing denial of service.

An excluded subdomain constraint in a certificate chain does not restrict the usage of wildcard SANs in the leaf certificate. For example a constraint that excludes the subdomain test.example.com does not prevent a leaf certificate from claiming the SAN *.example.com.

Validating certificate chains which contain DSA public keys can cause programs to panic, due to an interface cast that assumes they implement the Equal method. This affects programs which validate arbitrary certificate chains.