Internet Bug Bounty · Report #221790
Certificate message OOB reads (CVE-2016-6306)
Summary
In OpenSSL 1.0.2 and earlier some missing message length checks can result in OOB reads of up to 2 bytes beyond an allocated buffer. There is a theoretical DoS risk but this has not been observed in practice on common platforms.
The messages affected are client certificate, client certificate request and server certificate. As a result the attack can only be performed against a client or a server which enables client authentication.
OpenSSL 1.1.0 is not affected.
OpenSSL 1.0.2 users should upgrade to 1.0.2i OpenSSL 1.0.1 users should upgrade to 1.0.1u
This issue was reported to OpenSSL on 22nd August 2016 by Shi Lei (Gear Team, Qihoo 360 Inc.). The fix was developed by Stephen Henson of the OpenSSL development team.
How it was found
In OpenSSL 1.0.2 and earlier some missing message length checks can result in OOB reads of up to 2 bytes beyond an allocated buffer. There is a theoretical DoS risk but this has not been observed in practice on common platforms.
The messages affected are client certificate, client certificate request and server certificate. As a result the attack can only be performed against a client or a server which enables client authentication.