Asterisk Project Security Advisory - AST-2019-006

         Product        Asterisk                                              
         Summary        SIP request can change address of a SIP peer.         
    Nature of Advisory  Denial of Service                                     
      Susceptibility    Remote Unauthenticated Sessions                       
         Severity       Minor                                                 
      Exploits Known    No                                                    
       Reported On      October 17, 2019                                      
       Reported By      Andrey V. T.                                          
        Posted On       November 21, 2019                                     
     Last Updated On    November 21, 2019                                     
     Advisory Contact   bford AT sangoma DOT com                              
         CVE Name       CVE-2019-18790                                        

      Description     A SIP request can be sent to Asterisk that can change   
                      a SIP peer’s IP address. A REGISTER does not need to    
                      occur, and calls can be hijacked as a result. The only  
                      thing that needs to be known is the peer’s name;        
                      authentication details such as passwords do not need    
                      to be known. This vulnerability is only exploitable     
                      when the “nat” option is set to the default, or         
                      “auto_force_rport”.                                     
    Modules Affected  channels/chan_sip.c                                     

    Resolution  Using any other option value for “nat” will prevent the       
                attack (such as “nat=no” or “nat=force_rport”), but will      
                need to be tested on an individual basis to ensure that it    
                works for the user’s deployment. On the fixed versions of     
                Asterisk, it will no longer set the address of the peer       
                before authentication is successful when a SIP request comes  
                in.                                                           

                               Affected Versions       
                         Product                       Release  
                                                       Series   
                  Asterisk Open Source                  13.x    All releases  
                  Asterisk Open Source                  16.x    All releases  
                  Asterisk Open Source                  17.x    All releases  
                   Certified Asterisk                   13.21   All releases  

                                  Corrected In                   
                              Product                              Release    
                       Asterisk Open Source                        13.29.2    
                       Asterisk Open Source                        16.6.2     
                       Asterisk Open Source                        17.0.1     
                        Certified Asterisk                       13.21-cert5  

                                     Patches                         
                               SVN URL                                Revision   
  http://downloads.asterisk.org/pub/security/AST-2019-006-13.diff    Asterisk 13 
  http://downloads.asterisk.org/pub/security/AST-2019-006-16.diff    Asterisk 16 
  http://downloads.asterisk.org/pub/security/AST-2019-006-17.diff    Asterisk 17 
  http://downloads.asterisk.org/pub/security/AST-2019-006-13.21.diff Certified   
                                                                     Asterisk    
                                                                     13.21-cert5 

    Links  https://issues.asterisk.org/jira/browse/ASTERISK-28589             

    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-2019-006.pdf and             
    http://downloads.digium.com/pub/security/AST-2019-006.html                

                                Revision History
          Date          Editor                 Revisions Made                 
    October 22, 2019   Ben Ford  Initial Revision                             
    November 14, 2019  Ben Ford  Corrected and updated fields for             
                                 versioning, and added CVE                    
    November 21, 2019  Ben Ford  Added “Posted On” date                       

               Asterisk Project Security Advisory - AST-2019-006
               Copyright © 2019 Digium, Inc. All Rights Reserved.
  Permission is hereby granted to distribute and publish this advisory in its
                           original, unaltered form.