[asterisk-dev] AST-2012-014: Crashes due to large stack allocations when using TCP

Asterisk Security Team security at asterisk.org
Wed Jan 2 15:23:52 CST 2013

               Asterisk Project Security Advisory - AST-2012-014

         Product        Asterisk                                              
         Summary        Crashes due to large stack allocations when using     
    Nature of Advisory  Stack Overflow                                        
      Susceptibility    Remote Unauthenticated Sessions (SIP)                 
                        Remote Authenticated Sessions (XMPP, HTTP)            
         Severity       Critical                                              
      Exploits Known    No                                                    
       Reported On      7 November, 2012                                      
       Reported By      Walter Doekes                                         
        Posted On       2 January, 2013                                       
     Last Updated On    January 2, 2013                                       
     Advisory Contact   Mark Michelson <mmichelson AT digium DOT com>         
         CVE Name       CVE-2012-5976                                         

    Description  Asterisk has several places where messages received over     
                 various network transports may be copied in a single stack   
                 allocation. In the case of TCP, since multiple packets in a  
                 stream may be concatenated together, this can lead to large  
                 allocations that overflow the stack.                         
                 In the case of SIP, it is possible to do this before a       
                 session is established. Keep in mind that SIP over UDP is    
                 not affected by this vulnerability.                          
                 With HTTP and XMPP, a session must first be established      
                 before the vulnerability may be exploited. The XMPP          
                 vulnerability exists both in the res_jabber.so module in     
                 Asterisk 1.8, 10, and 11 as well as the res_xmpp.so module   
                 in Asterisk 11.                                              

    Resolution  Stack allocations when using TCP have either been eliminated  
                in favor of heap allocations or have had an upper bound       
                placed on them to ensure that the stack will not overflow.    
                For SIP, the allocation now has an upper limit.               
                For HTTP, the allocation is now a heap allocation instead of  
                a stack allocation.                                           
                For XMPP, the allocation has been eliminated since it was     

                               Affected Versions
            Product           Release Series    
     Asterisk Open Source          1.8.x        All versions                  
     Asterisk Open Source          10.x         All versions                  
     Asterisk Open Source          11.x         All versions                  
      Certified Asterisk          1.8.11        SIP: unaffected               
                                                HTTP and XMPP: All versions   
     Asterisk Digiumphones   10.x-digiumphones  All versions                  

                                  Corrected In
                 Product                              Release                 
          Asterisk Open Source     , 10.11.1, 11.1.1        
           Certified Asterisk                      1.8.11-cert10              
          Asterisk Digiumphones                10.11.1-digiumphones           

                               SVN URL                              Revision  
   http://downloads.asterisk.org/pub/security/AST-2012-014-1.8.diff Asterisk  
   http://downloads.asterisk.org/pub/security/AST-2012-014-10.diff  Asterisk  
   http://downloads.asterisk.org/pub/security/AST-2012-014-11.diff  Asterisk  

       Links     https://issues.asterisk.org/jira/browse/ASTERISK-20658       

    Asterisk Project Security Advisories are posted at                        
    This document may be superseded by later versions; if so, the latest      
    version will be posted at                                                 
    http://downloads.digium.com/pub/security/AST-2012-014.pdf and             

                                Revision History
          Date              Editor                 Revisions Made             
    19 November, 2012  Mark Michelson    Initial Draft                        
    02 January, 2013   Matt Jordan       Removed ABE from affected products   

               Asterisk Project Security Advisory - AST-2012-014
              Copyright (c) 2012 Digium, Inc. All Rights Reserved.
  Permission is hereby granted to distribute and publish this advisory in its
                           original, unaltered form.

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