Apache Thrift, Apache Thrift: The C++ and D clients fall back to the certificate Common Name when subjectAltName entries are present but do not match

Improper Validation of Certificate with Host Mismatch in the C++ and D libraries of Apache Thrift.

Both libraries install a default access manager for client sockets — TSSLSocketFactory does so in C++, and the accessManager property does so in D — which compares the peer certificate against the host

name that was connected to. That comparison walks the subjectAltName dNSName entries first and consults the certificate Common Name afterwards. A name that does not match yields a "skip" result rather than

a rejection, so a certificate whose subjectAltName entries are all present and all non-matching falls through to the Common Name, which can then satisfy the check.

RFC 6125 section 6.4.4, and RFC 9525 section 2, require that the Common Name is not consulted when a dNSName subjectAltName is present. A certificate carrying subjectAltName entries for one name and a

Common Name for another is therefore accepted for a connection to the second name.

Exploitation requires an attacker positioned on the network path who holds a certificate that chains to a certificate authority in the client's trust store and whose Common Name matches the connected host

name. Public certificate authorities have not issued on Common Name alone for many years, so this is principally a concern for deployments using a private or enterprise public-key infrastructure.

This issue affects the C++ library of Apache Thrift from 0.7.0 through 0.24.0 and the D library from 0.9.0 through 0.24.0. Users should upgrade to 0.25.0.