CVE-2019-1559

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).

1 For this issue to be exploitable, the (server) application using the OpenSSL library needs to use it incorrectly. 2. There are multiple other requirements for the attack to succeed: - The ciphersuite used must be obsolete CBC cipher without a stitched implementation (or the system be in FIPS mode) - the attacker has to be a MITM - the attacker has to be able to control the client side to send requests to the buggy server on demand

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

As a workaround you can disable SHA384 if applications (compiled with OpenSSL) allow for adjustment of the ciphersuite string configuration.