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AA-2008.0003                  AUSCERT Advisory

                               [UNIX/Linux]
             Asterisk 1.4.17 released to fix SIP vulnerability
                              9 January 2008
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        AusCERT Advisory Summary
        ------------------------

Product:              Asterisk 1.4.x before 1.4.17
Operating System:     UNIX variants (UNIX, Linux, OSX)
Impact:               Denial of Service
Access:               Remote/Unauthenticated
CVE Names:            CVE-2008-0095
Member content until: Wednesday, February 06 2008


OVERVIEW:

        A vulnerability has been reported in Asterisk 1.4.x prior to 
        1.4.17 that can result in a remotely exploited Denial of 
        Service (DoS).

IMPACT:

        The National Vulnerability Database [1], gives the following
        information regarding these vulnerabilities:

        o CVE-2008-0095: "The SIP channel driver in Asterisk Open Source 
          1.4.x before 1.4.17, Business Edition before C.1.0-beta8, 
          AsteriskNOW before beta7, Appliance Developer Kit before Asterisk 
          1.4 revision 95946, and Appliance s800i 1.0.x before 1.0.3.4 
          allows remote attackers to cause a denial of service (daemon 
          crash) via a BYE message with an Also (Also transfer) header, 
          which triggers a NULL pointer dereference." [2]

        Asterisk.org also added the following: 

        "This issue requires an authenticated session that allows transfers 
        to be exploited. If unauthenticated calls with transfer capability 
        are allowed, then this issue could be exploited with an 
        unauthenticated session. Also, this issue only affects Asterisk 
        1.4. Asterisk 1.2 is not affected. Systems that do not use chan_sip 
        are also not affected." [3]


MITIGATION:

        This issue has been corrected in the release of Asterisk 1.4.17, 
        which is available for download from the Asterisk website. [4]


REFERENCES:

        [1] National Vulnerability Database
            http://nvd.nist.gov/

        [2] National Vulnerability Database (CVE-2008-0095)
            http://nvd.nist.gov/nvd.cfm?cvename=CVE-2008-0095

        [3] Asterisk 1.4.17 Released
            http://www.asterisk.org/node/48442
 
        [4] Asterisk Downloads
            http://www.asterisk.org/downloads


AusCERT has made every effort to ensure that the information contained
in this document is accurate.  However, the decision to use the information
described is the responsibility of each user or organisation. The decision to
follow or act on information or advice contained in this security bulletin is
the responsibility of each user or organisation, and should be considered in
accordance with your organisation's site policies and procedures. AusCERT
takes no responsibility for consequences which may arise from following or
acting on information or advice contained in this security bulletin.

If you believe that your computer system has been compromised or attacked in 
any way, we encourage you to let us know by completing the secure National IT 
Incident Reporting Form at:

        http://www.auscert.org.au/render.html?it=3192

===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
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