The OpenSSL project has disclosed a new certificate validation vulnerability. “During certificate verification, OpenSSL (starting from version 1.0.1n and 1.0.2b) will attempt to find an alternative certificate chain if the first attempt to build such a chain fails. An error in the implementation of this logic can mean that an attacker could cause certain checks on untrusted certificates to be bypassed, such as the CA flag, enabling them to use a valid leaf certificate to act as a CA and ‘issue’ an invalid certificate.” This is thus a client-side, man-in-the-middle vulnerability.
Read more at LWN
