On BIG-IP 11.5.1-11.5.4, 11.6.1, and 12.1.0, a virtual server configured with a Client SSL profile may be vulnerable to a chosen ciphertext attack against CBC ciphers. When exploited, this may result in plaintext recovery of encrypted messages through a man-in-the-middle (MITM) attack, despite the attacker not having gained access to the server's private key itself. (CVE-2019-6593 also known as Zombie POODLE and GOLDENDOODLE.)

If an application encounters a fatal protocol error and then calls SSL_shutdown() twice (once to send a close_notify, and once to receive one) 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 (applications should not do this but some do anyway). Fixed in OpenSSL 1.0.2r (Affected 1.0.2-1.0.2q).