Secunia

A weakness has been reported in Asterisk, which can be exploited by malicious people to determine valid user names.

The weakness is caused due to Asterisk returning different responses when rejecting INVITE or REGISTER requests depending on whether or not a valid user name is supplied. This can be exploited to enumerate valid user names.

The weakness is reported in the following products and versions:
* Asterisk Open Source 1.2.x versions prior to 1.2.32
* Asterisk Open Source 1.4.x versions prior to 1.4.24.1
* Asterisk Open Source 1.6.0.x versions prior to 1.6.0.8
* Asterisk Business Edition A.x.x all versions
* Asterisk Business Edition B.x.x versions prior to B.2.5.8
* Asterisk Business Edition C.1.x.x versions prior to C.1.10.5
* Asterisk Business Edition C.2.x.x versions prior to C.2.3.3
* s800i (Asterisk Appliance) 1.3.x versions prior to 1.3.0.2

Solution
Asterisk Open Source:
Further details available in Customer Area

Provided and/or discovered by
The vendor credits Kerin Millar and Fergal Glynn.

Original Advisory
http://downloads.digium.com/pub/security/AST-2009-003.html

Deep Links
Links available in Customer Area