The init_nss_hash function in exec/totemcrypto.c in Corosync 2.0 before 2.3 does not properly initialize the HMAC key, which allows remote attackers to cause a denial of service (crash) via a crafted packet.
http://secunia.com/advisories/52037
http://seclists.org/oss-sec/2013/q1/214