Severity Medium
Remote Yes
Type Information disclosure
A padding oracle has been found in OpenSSL versions prior to 1.0.2r. This issue does not impact OpenSSL 1.1.1 or 1.1.0. 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). AEAD ciphersuites are not impacted.
Group Package Affected Fixed Severity Status Ticket
AVG-918 lib32-openssl-1.0 1.0.2.q-1 1.0.2.r-1 Medium Fixed
AVG-917 openssl-1.0 1.0.2.q-1 1.0.2.r-1 Medium Fixed
Date Advisory Group Package Severity Description
03 Mar 2019 ASA-201903-6 AVG-918 lib32-openssl-1.0 Medium information disclosure
02 Mar 2019 ASA-201903-2 AVG-917 openssl-1.0 Medium information disclosure