Debian DLA-1701-1 : openssl security update
Medium Nessus Plugin ID 122549
SynopsisThe remote Debian host is missing a security update.
DescriptionJuraj Somorovsky, Robert Merget and Nimrod Aviram discovered a padding oracle attack in OpenSSL.
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.
For Debian 8 'Jessie', this problem has been fixed in version 1.0.1t-1+deb8u11.
We recommend that you upgrade your openssl packages.
NOTE: Tenable Network Security has extracted the preceding description block directly from the DLA security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
SolutionUpgrade the affected packages.