IAX2 in Asterisk Open Source 1.2.x before 1.2.31, 1.4.x before 1.4.23-rc4, and 1.6.x before 1.6.0.3-rc2; Business Edition A.x.x, B.x.x before B.2.5.7, C.1.x.x before C.1.10.4, and C.2.x.x before C.2.1.2.1; and s800i 1.2.x before 1.3.0 responds differently to a failed login attempt depending on whether the user account exists, which allows remote attackers to enumerate valid usernames.
Asterisk Open Source 1.2.26 through 1.2.30.3 and Business Edition B.2.3.5 through B.2.5.5, when realtime IAX2 users are enabled, allows remote attackers to cause a denial of service (crash) via authentication attempts involving (1) an unknown user or (2) a user using hostname matching.
A denial of service flaw was found in the way asterisk processed certain requests to negotiate secure video stream, when the ressrtp Asterisk module has been loaded and video support has not been enabled. A remote attacker could provide a specially-crafted media stream negotiation request, which once processed by Asterisk would lead to asterisk daemon crash by processing crypto line for such media stream.
References: [1] http://downloads.asterisk.org/pub/security/AST-2012-001.html [2] https://issues.asterisk.org/jira/browse/ASTERISK-19202
Upstream patch against the v1.8.x branch: [3] http://downloads.asterisk.org/pub/security/AST-2012-001-1.8.diff
Upstream patch against the v1.10.x branch: [4] http://downloads.asterisk.org/pub/security/AST-2012-001-10.diff
chanskinny.c in the Skinny (aka SCCP) channel driver in Certified Asterisk 1.8.11-cert before 1.8.11-cert2 and Asterisk Open Source 1.8.x before 1.8.12.1 and 10.x before 10.4.1 allows remote authenticated users to cause a denial of service (NULL pointer dereference and daemon crash) by closing a connection in off-hook mode.
asterisk allows calls on prohibited networks
A memory exhaustion vulnerability exists in Asterisk Open Source 13.x before 13.15.1 and 14.x before 14.4.1 and Certified Asterisk 13.13 before 13.13-cert4, which can be triggered by sending specially crafted SCCP packets causing an infinite loop and leading to memory exhaustion (by message logging in that loop).
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.