Multiple buffer overflows in Asterisk Open Source 1.4.x before 1.4.18.1 and 1.4.19-rc3, Open Source 1.6.x before 1.6.0-beta6, Business Edition C.x.x before C.1.6.1, AsteriskNOW 1.0.x before 1.0.2, Appliance Developer Kit before 1.4 revision 109386, and s800i 1.1.x before 1.1.0.2 allow remote attackers to (1) write a zero to an arbitrary memory location via a large RTP payload number, related to the ast_rtp_unset_m_type function in main/rtp.c; or (2) write certain integers to an arbitrary memory location via a large number of RTP payloads, related to the process_sdp function in channels/chan_sip.c.

Unspecified vulnerability in Asterisk Open Source 1.2.x before 1.2.27, 1.4.x before 1.4.18.1 and 1.4.19-rc3; Business Edition A.x.x, B.x.x before B.2.5.1, and C.x.x before C.1.6.2; AsteriskNOW 1.0.x before 1.0.2; Appliance Developer Kit before 1.4 revision 109393; and s800i 1.0.x before 1.1.0.2; allows remote attackers to access the SIP channel driver via a crafted From header.

The SIP channel driver in Asterisk Open Source 1.4.x before 1.4.17, Business Edition before C.1.0-beta8, AsteriskNOW before beta7, Appliance Developer Kit before Asterisk 1.4 revision 95946, and Appliance s800i 1.0.x before 1.0.3.4 allows remote attackers to cause a denial of service (daemon crash) via a BYE message with an Also (Also transfer) header, which triggers a NULL pointer dereference.

Asterisk Open Source 1.2.x before 1.2.26 and 1.4.x before 1.4.16, and Business Edition B.x.x before B.2.3.6 and C.x.x before C.1.0-beta8, when using database-based registrations ("realtime") and host-based authentication, does not check the IP address when the username is correct and there is no password, which allows remote attackers to bypass authentication using a valid username.