Some vulnerabilities have been reported in Asterisk, which can be exploited by malicious people to cause a DoS (Denial of Service).

The vulnerabilities are caused due to NULL-pointer dereference errors in the "sip_uri_params_cmp()" and "sip_uri_headers_cmp()" functions. This can be exploited to crash the application via a SIP message lacking certain headers or parameters in the SIP URI.

Successful exploitation requires a valid user account on the Asterisk server or a Man-in-the-Middle attack. It also requires that the SIP channel driver is configured with the "pedantic" option enabled.

The vulnerabilities are reported in Asterisk Open Source versions 1.4.22, 1.4.23, 1.4.23.1, all 1.6.0.x versions prior to 1.6.0.6, all 1.6.1.x versions prior to 1.6.1.0-rc2, and Asterisk Business Edition version C.2.3.

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

Provided and/or discovered by
The vendor credits bugs.digium.com user klaus3000.

Changelog
Further details available to Secunia VIM customers

Original Advisory
http://downloads.digium.com/pub/security/AST-2009-002.html

Alternate/detailed remediation
Further details available in Customer Area

Deep Links
Links available to Secunia VIM customers