The remote host is missing an update to the system as announced in the referenced advisory.
Update your system with the appropriate patches or software upgrades. http://downloads.asterisk.org/pub/security/AST-2011-008.html http://downloads.asterisk.org/pub/security/AST-2011-009.html http://downloads.asterisk.org/pub/security/AST-2011-010.html http://downloads.asterisk.org/pub/security/AST-2011-011.html http://www.vuxml.org/freebsd/40544e8c-9f7b-11e0-9bec-6c626dd55a41.html
The following packages are affected: asterisk14 asterisk16 asterisk18 CVE-2011-2529 chan_sip.c in the SIP channel driver in Asterisk Open Source 1.6.x before 22.214.171.124.1 and 1.8.x before 126.96.36.199 does not properly handle '\0' characters in SIP packets, which allows remote attackers to cause a denial of service (memory corruption) or possibly have unspecified other impact via a crafted packet. CVE-2011-2535 chan_iax2.c in the IAX2 channel driver in Asterisk Open Source 1.4.x before 188.8.131.52, 1.6.2.x before 184.108.40.206.1, and 1.8.x before 220.127.116.11, and Asterisk Business Edition C.3 before C.3.7.3, accesses a memory address contained in an option control frame, which allows remote attackers to cause a denial of service (daemon crash) or possibly have unspecified other impact via a crafted frame. CVE-2011-2536 chan_sip.c in the SIP channel driver in Asterisk Open Source 1.4.x before 18.104.22.168, 1.6.2.x before 22.214.171.124.2, and 1.8.x before 126.96.36.199, and Asterisk Business Edition C.3.x before C.3.7.3, disregards the alwaysauthreject option and generates different responses for invalid SIP requests depending on whether the user account exists, which allows remote attackers to enumerate account names via a series of requests.