A microprocessor side-channel vulnerability was found on SMT architectures. An attacker running a malicious process on the same core of the processor as the victim process can extract certain secret information. If an application encounters a fatal protocol error and then calls SSL_shutdown twice then OpenSSL can respond differently to the calling application if a 0 byte record is received with invalid padding compared to if a 0 byte record is received with an invalid MAC. If the application then behaves differently based on that in a way that is detectable to the remote peer, then this amounts to a padding oracle that could be used to decrypt data. In order for this to be exploitable "non-stitched" ciphersuites must be in use. Stitched ciphersuites are optimised implementations of certain commonly used ciphersuites. Also the application must call SSL_shutdown twice even if a protocol error has occurred