Some vulnerabilities have been reported in Asterisk, which can be exploited by malicious people to bypass certain security restrictions, cause a DoS (Denial of Service), and potentially compromise a vulnerable system.

1) An error within the "ast_rtp_unset_m_type()" function in main/rtp.c when handling of RTP codec payloads can be exploited to write a 0 into certain memory locations by sending a specially crafted SIP packet with SDP containing a payload number greater than 256.

2) A boundary error within the "process_sdp()" function in channels/chan_sip.c when handling of RTP codec payloads can be exploited to cause a stack-based buffer overflow by sending more than 32 RTP payloads.

3) An error within the SIP channel driver when determining if authentication is required can be exploited to perform unauthenticated calls by sending specially crafted From headers to the driver.

Note: A format string error within the "ast_verbose()" logging API call has also been reported by Steve Davies and Brandon Kruse. This can be exploited to crash the application by providing input containing format specifiers, which is later used in the affected API call. However, this only affects Asterisk 1.6.x versions prior to 1.6.0-beta6.

Solution
Update to a fixed version.
Further details available to Secunia VIM customers

Provided and/or discovered by
1, 2) Mu Security Research Team
3) Jason Parker

Changelog
Further details available to Secunia VIM customers

Original Advisory
Digium:
http://downloads.digium.com/pub/security/AST-2008-002.html
http://downloads.digium.com/pub/security/AST-2008-003.html
http://downloads.digium.com/pub/security/AST-2008-004.html

Mu Security:
http://labs.musecurity.com/advisories/MU-200803-01.txt

Deep Links
Links available to Secunia VIM customers