Debian Security Advisory
DLA-1701-1 openssl -- LTS security update
- Date Reported:
- 01 Mar 2019
- Affected Packages:
- Security database references:
- In Mitre's CVE dictionary: CVE-2019-1559.
- More information:
Juraj 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.
Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: https://wiki.debian.org/LTS