Amazon Linux AMI Security Advisory: ALAS-2019-1188
Advisory Release Date: 2019-04-04 19:13 Pacific
Advisory Updated Date: 2019-04-09 16:10 Pacific
A microprocessor side-channel vulnerability was found on SMT (e.g, Hyper-Threading) architectures. An attacker running a malicious process on the same core of the processor as the victim process can extract certain secret information. (CVE-2018-5407)
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).
Run yum update openssl to update your system.