Secunia

A vulnerability has been reported in Asterisk, which can be exploited by malicious people to cause a DoS (Denial of Service).

The vulnerability is caused due to the call number field in a messages being handled as a fixed size 15 bit field. This can be exploited to exhaust all available call numbers via a large number of messages and prevent the handling of further sessions.

The vulnerability is reported in the following products and versions:
* Asterisk Open Source 1.2.x all versions
* Asterisk Open Source 1.4.x all versions
* Asterisk Open Source 1.6.x all versions
* Asterisk Business Edition B.x.x all versions
* Asterisk Business Edition C.x.x all versions
* s800i (Asterisk Appliance) 1.3.x all versions

Solution
Update to the latest versions or apply patches, and consult the users guide section of the IAX2 Security document.
Further details available in Customer Area

Provided and/or discovered by
The vendor credits:
* Noam Rathaus
* Blake Cornell

Original Advisory
http://downloads.asterisk.org/pub/security/AST-2009-006.html

Deep Links
Links available in Customer Area