A flaw in the DTLS SRTP extension parsing code allows an attacker, who sends a carefully crafted handshake message, to cause OpenSSL to fail to free up to 64k of memory causing a memory leak. This could be exploited in a Denial Of Service attack. This issue affects OpenSSL 1.0.1 server implementations for both SSL/TLS and DTLS regardless of whether SRTP is used or configured. Implementations of OpenSSL that have been compiled with OPENSSL_NO_SRTP defined are not affected.
When an OpenSSL SSL/TLS/DTLS server receives a session ticket the integrity of that ticket is first verified. In the event of a session ticket integrity check failing, OpenSSL will fail to free memory causing a memory leak. By sending a large number of invalid session tickets an attacker could exploit this issue in a Denial Of Service attack.
When OpenSSL is configured with "no-ssl3" as a build option, servers could accept and complete a SSL 3.0 handshake, and clients could be configured to send them.
OpenSSL has added support for TLS_FALLBACK_SCSV to allow applications to block the ability for a MITM attacker to force a protocol downgrade.
Some client applications (such as browsers) will reconnect using a downgraded protocol to work around interoperability bugs in older servers. This could be exploited by an active man-in-the-middle to downgrade connections to SSL 3.0 even if both sides of the connection support higher protocols. SSL 3.0 contains a number of weaknesses including POODLE (CVE-2014-3566).