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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                       ESB-2008.0415 -- [UNIX/Linux]
             Asterisk Project Security Advisory - AST-2008-006
                               30 April 2008

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:              Asterisk Open Source prior to 1.2.28
                      Asterisk Open Source prior to 1.4.20 
                      Asterisk Business Edition prior to B.2.5.2
                      Asterisk Business Edition prior to C.1.8.1 
                      AsteriskNOW prior to 1.0.3 
                      s800i (Asterisk Appliance) prior to 1.1.0.3
Publisher:            Digium
Operating System:     UNIX variants (UNIX, Linux, OSX)
Impact:               Denial of Service
Access:               Remote/Unauthenticated
CVE Names:            CVE-2008-1897 CVE-2008-1923

Original Bulletin:  
  http://downloads.digium.com/pub/security/AST-2008-006.html 

Revision History:     April 30 2008: Added CVE
                      April 24 2008: Initial Release

- --------------------------BEGIN INCLUDED TEXT--------------------


               Asterisk Project Security Advisory - AST-2008-006

   +------------------------------------------------------------------------+
   |      Product       | Asterisk                                          |
   |--------------------+---------------------------------------------------|
   |      Summary       | 3-way handshake in IAX2 incomplete                |
   |--------------------+---------------------------------------------------|
   | Nature of Advisory | Remote amplification attack                       |
   |--------------------+---------------------------------------------------|
   |   Susceptibility   | Remote unauthenticated sessions                   |
   |--------------------+---------------------------------------------------|
   |      Severity      | Critical                                          |
   |--------------------+---------------------------------------------------|
   |   Exploits Known   | Yes                                               |
   |--------------------+---------------------------------------------------|
   |    Reported On     | April 18, 2008                                    |
   |--------------------+---------------------------------------------------|
   |    Reported By     | Joel R. Voss aka. Javantea < jvoss AT altsci DOT  |
   |                    | com >                                             |
   |--------------------+---------------------------------------------------|
   |     Posted On      | April 22, 2008                                    |
   |--------------------+---------------------------------------------------|
   |  Last Updated On   | April 22, 2008                                    |
   |--------------------+---------------------------------------------------|
   |  Advisory Contact  | Tilghman Lesher < tlesher AT digium DOT com >     |
   |--------------------+---------------------------------------------------|
   |      CVE Name      | CVE-2008-1897                                     |
   +------------------------------------------------------------------------+

   +------------------------------------------------------------------------+
   | Description | Javantea originally reported an issue in IAX2, whereby   |
   |             | an attacker could send a spoofed IAX2 NEW message, and   |
   |             | Asterisk would start sending early audio to the target   |
   |             | address, without ever receiving an initial response.     |
   |             | That original vulnerability was addressed in June 2007,  |
   |             | by requiring a response to the initial NEW message       |
   |             | before starting to send any audio.                       |
   |             |                                                          |
   |             | Javantea subsequently found that we were doing           |
   |             | insufficent verification of the ACK response and that    |
   |             | the ACK response could be spoofed, just like the initial |
   |             | NEW message. We have addressed this failure with two     |
   |             | changes. First, we have started to require that the ACK  |
   |             | response contains the unique source call number that we  |
   |             | send in our reply to the NEW message. Any ACK response   |
   |             | that does not contain the source call number that we     |
   |             | have created will be silently thrown away. Second, we    |
   |             | have made the generation of our source call number a     |
   |             | little more difficult to predict, by randomly selecting  |
   |             | a source call number, instead of allocating them         |
   |             | sequentially.                                            |
   +------------------------------------------------------------------------+

   +------------------------------------------------------------------------+
   | Workaround | Disable remote unauthenticated IAX2 sessions, by          |
   |            | disallowing guest access.                                 |
   +------------------------------------------------------------------------+

   +------------------------------------------------------------------------+
   | Resolution | Upgrade your Asterisk installation to revision 114561 or  |
   |            | later, or install one of the releases shown below.        |
   +------------------------------------------------------------------------+

   +------------------------------------------------------------------------+
   | Commentary | We would like to thank Javantea for notifying us of this  |
   |            | problem; however, we note that he posted exploit code     |
   |            | prior to that notification, which is considered           |
   |            | irresponsible behavior in the whitehat security industry. |
   |            | In the future, advance notice of any such release would   |
   |            | be appreciated.                                           |
   +------------------------------------------------------------------------+

   +------------------------------------------------------------------------+
   |                           Affected Versions                            |
   |------------------------------------------------------------------------|
   |            Product            |  Release   |                           |
   |                               |   Series   |                           |
   |-------------------------------+------------+---------------------------|
   |     Asterisk Open Source      |   1.0.x    | All versions              |
   |-------------------------------+------------+---------------------------|
   |     Asterisk Open Source      |   1.2.x    | All versions prior to     |
   |                               |            | 1.2.28                    |
   |-------------------------------+------------+---------------------------|
   |     Asterisk Open Source      |   1.4.x    | All versions prior to     |
   |                               |            | 1.4.20                    |
   |-------------------------------+------------+---------------------------|
   |   Asterisk Business Edition   |   A.x.x    | All versions              |
   |-------------------------------+------------+---------------------------|
   |   Asterisk Business Edition   |   B.x.x    | All versions prior to     |
   |                               |            | B.2.5.2                   |
   |-------------------------------+------------+---------------------------|
   |   Asterisk Business Edition   |   C.x.x    | All versions prior to     |
   |                               |            | C.1.8.1                   |
   |-------------------------------+------------+---------------------------|
   |          AsteriskNOW          |   1.0.x    | All versions prior to     |
   |                               |            | 1.0.3                     |
   |-------------------------------+------------+---------------------------|
   | Asterisk Appliance Developer  |   0.x.x    | All versions              |
   |              Kit              |            |                           |
   |-------------------------------+------------+---------------------------|
   |  s800i (Asterisk Appliance)   |   1.0.x    | All versions prior to     |
   |                               |            | 1.1.0.3                   |
   +------------------------------------------------------------------------+

   +------------------------------------------------------------------------+
   |                              Corrected In                              |
   |------------------------------------------------------------------------|
   |                   Product                   |         Release          |
   |---------------------------------------------+--------------------------|
   |            Asterisk Open Source             |          1.2.28          |
   |---------------------------------------------+--------------------------|
   |            Asterisk Open Source             |          1.4.20          |
   |---------------------------------------------+--------------------------|
   |          Asterisk Business Edition          |         B.2.5.2          |
   |---------------------------------------------+--------------------------|
   |          Asterisk Business Edition          |         C.1.8.1          |
   |---------------------------------------------+--------------------------|
   |                 AsteriskNOW                 |          1.0.3           |
   |---------------------------------------------+--------------------------|
   |         s800i (Asterisk Appliance)          |         1.1.0.3          |
   +------------------------------------------------------------------------+

   +------------------------------------------------------------------------+
   |   Links    | https://www.altsci.com/concepts/page.php?s=asteri&p=2     |
   +------------------------------------------------------------------------+

   +------------------------------------------------------------------------+
   | Asterisk Project Security Advisories are posted at                     |
   | http://www.asterisk.org/security                                       |
   |                                                                        |
   | This document may be superseded by later versions; if so, the latest   |
   | version will be posted at                                              |
   | http://downloads.digium.com/pub/security/AST-2008-006.pdf and          |
   | http://downloads.digium.com/pub/security/AST-2008-006.html             |
   +------------------------------------------------------------------------+

   +------------------------------------------------------------------------+
   |                            Revision History                            |
   |------------------------------------------------------------------------|
   |        Date         |        Editor        |      Revisions Made       |
   |---------------------+----------------------+---------------------------|
   | April 22, 2008      | Tilghman Lesher      | Initial release           |
   +------------------------------------------------------------------------+

               Asterisk Project Security Advisory - AST-2008-006
              Copyright (c) 2008 Digium, Inc. All Rights Reserved.
  Permission is hereby granted to distribute and publish this advisory in its
                           original, unaltered form.

- --------------------------END INCLUDED TEXT--------------------

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