Asterisk Project Security Advisory – During pedantic SIP processing the From header value is passed to the ast_uri_decode function to be decoded. In two instances it is possible for the code to cause a crash as the From header value is not checked to be non-NULL before being passed to the function.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/66961/AST-2008-008.txt
Source: https://packetstormsecurity.com/files/66961/AST-2008-008.txt.html