[asterisk-security] AST-2018-001: Crash when receiving unnegotiated dynamic payload

[Asterisk Security Team]

               Asterisk Project Security Advisory - AST-2018-001

          Product         Asterisk                                            
          Summary         Crash when receiving unnegotiated dynamic payload   
     Nature of Advisory   Remote Crash                                        
       Susceptibility     Remote Unauthenticated Sessions                     
          Severity        Major                                               
       Exploits Known     No                                                  
        Reported On       December 18, 2017                                   
        Reported By       Sébastien Duthil                                    
         Posted On        February 21, 2018                                   
      Last Updated On     February 21, 2018                                   
      Advisory Contact    Joshua Colp <jcolp AT digium DOT com>               
          CVE Name       CVE-2018-7285                                        

    Description  The RTP support in Asterisk maintains its own registry of    
                 dynamic codecs and desired payload numbers. While an SDP     
                 negotiation may result in a codec using a different payload  
                 number these desired ones are still stored internally. When  
                 an RTP packet was received this registry would be consulted  
                 if the payload number was not found in the negotiated SDP.   
                 This registry was incorrectly consulted for all packets,     
                 even those which are dynamic. If the payload number          
                 resulted in a codec of a different type than the RTP stream  
                 (for example the payload number resulted in a video codec    
                 but the stream carried audio) a crash could occur if no      
                 stream of that type had been negotiated. This was due to     
                 the code incorrectly assuming that a stream of the type      
                 would always exist.                                          

    Resolution  The RTP support will now only consult the registry for        
                payloads which are statically defined. The core has also      
                been changed to protect against situations where a frame of   
                media is received for a media type that has not been          
                negotiated.                                                   
                                                                              
                To receive these fixes update to the given version of         
                Asterisk or apply the provided patch. There is no             
                configuration which can protect against this vulnerability.   

                               Affected Versions
                Product              Release Series  
         Asterisk Open Source             13.x       Unaffected               
         Asterisk Open Source             14.x       Unaffected               
         Asterisk Open Source             15.x       All versions             
          Certified Asterisk             13.18       Unaffected               

                                  Corrected In  
                     Product                              Release             
               Asterisk Open Source                        15.2.2             

                                    Patches                        
                               SVN URL                              Revision  
   http://downloads.asterisk.org/pub/security/AST-2018-001-15.diff Asterisk   
                                                                   15         

       Links     https://issues.asterisk.org/jira/browse/ASTERISK-27488       

    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-2018-001.pdf and             
    http://downloads.digium.com/pub/security/AST-2018-001.html                

                                Revision History
          Date                 Editor                  Revisions Made         
    January 15, 2018   Joshua Colp              Initial Revision              
    February 21, 2018  Joshua Colp              Added CVE                     

               Asterisk Project Security Advisory - AST-2018-001
               Copyright © 2018 Digium, Inc. All Rights Reserved.
  Permission is hereby granted to distribute and publish this advisory in its
                           original, unaltered form.