rtp.c in Asterisk Open Source 1.2.x before 1.2.37, 1.4.x before 1.4.27.1, 1.6.0.x before 1.6.0.19, and 1.6.1.x before 1.6.1.11; Business Edition B.x.x before B.2.5.13, C.2.x.x before C.2.4.6, and C.3.x.x before C.3.2.3; and s800i 1.3.x before 1.3.0.6 allows remote attackers to cause a denial of service (daemon crash) via an RTP comfort noise payload with a long data length.

Asterisk Open Source 1.2.x before 1.2.35, 1.4.x before 1.4.26.3, 1.6.0.x before 1.6.0.17, and 1.6.1.x before 1.6.1.9; Business Edition A.x.x, B.x.x before B.2.5.12, C.2.x.x before C.2.4.5, and C.3.x.x before C.3.2.2; AsteriskNOW 1.5; and s800i 1.3.x before 1.3.0.5 generate different error messages depending on whether a SIP username is valid, which allows remote attackers to enumerate valid usernames via multiple crafted REGISTER messages with inconsistent usernames in the URI in the To header and the Digest in the Authorization header.

The SIP channel driver in Asterisk Open Source 1.2.x before 1.2.34, 1.4.x before 1.4.26.1, 1.6.0.x before 1.6.0.12, and 1.6.1.x before 1.6.1.4; Asterisk Business Edition A.x.x, B.x.x before B.2.5.9, C.2.x before C.2.4.1, and C.3.x before C.3.1; and Asterisk Appliance s800i 1.2.x before 1.3.0.3 does not use a maximum width when invoking sscanf style functions, which allows remote attackers to cause a denial of service (stack memory consumption) via SIP packets containing large sequences of ASCII decimal characters, as demonstrated via vectors related to (1) the CSeq value in a SIP header, (2) large Content-Length value, and (3) SDP.