Asterisk 1.4 before 1.4.1 and 1.2 before 1.2.16 allows remote attackers to cause a denial of service (crash) by sending a Session Initiation Protocol (SIP) packet without a URI and SIP-version header, which results in a NULL pointer dereference.

Unspecified vulnerability in the SIP channel driver (channels/chan_sip.c) in Asterisk 1.2.x before 1.2.13 and 1.4.x before 1.4.0-beta3 allows remote attackers to cause a denial of service (resource consumption) via unspecified vectors that result in the creation of "a real pvt structure" that uses more resources than necessary.