chan_sip.c in Asterisk Open Source 1.8.x before 1.8.8.2 and 10.x before 10.0.1, when the res_srtp module is used and media support is improperly configured, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted SDP message with a crypto attribute and a (1) video or (2) text media type, as demonstrated by CSipSimple.
Gentoo Linux Security Advisory 201202-6 - A vulnerability in Asterisk could allow a remote attacker to cause a Denial of Service condition. Versions less than 1.8.8.2 are affected.