OpenSSL 1.0.1 and 1.0.2-beta1 security upgrades

An attacker using a carefully crafted handshake can force the use of weak keying material in OpenSSL SSL/TLS clients and servers. This can be exploited by a Man-in-the-middle (MITM) attack where the attacker can decrypt and modify traffic from the attacked client and server.

The attack can only be performed between a vulnerable client *and* server. OpenSSL clients are vulnerable in all versions of OpenSSL. Servers are only known to be vulnerable in OpenSSL 1.0.1 and 1.0.2-beta1. Users of OpenSSL servers earlier than 1.0.1 are advised to upgrade as a precaution.

By sending an invalid DTLS handshake to an OpenSSL DTLS client the code can be made to recurse eventually crashing in a DoS attack.

A buffer overrun attack can be triggered by sending invalid DTLS fragments to an OpenSSL DTLS client or server. This is potentially exploitable to run arbitrary code on a vulnerable client or server.

A flaw in the do_ssl3_write function can allow remote attackers to cause a denial of service via a NULL pointer dereference. This flaw only affects OpenSSL 1.0.0 and 1.0.1 where SSL_MODE_RELEASE_BUFFERS is enabled, which is not the default and not common.

A race condition in the ssl3_read_bytes function can allow remote attackers to inject data across sessions or cause a denial of service. This flaw only affects multithreaded applications using OpenSSL 1.0.0 and 1.0.1, where SSL_MODE_RELEASE_BUFFERS is enabled, which is not the default and not common.

OpenSSL TLS clients enabling anonymous ECDH ciphersuites are subject to a denial of service attack.