Cisco PPTP DoS Details?

[Dragos Ruiu <dr () kyx net>]

Does anyone have any further details of this or any info sufficient to build a
signature for this? Alerting on all pptp packets to your ciscos doesn't seem
like the right thing to do....

thanks,
--dr

url: http://www.cisco.com/warp/public/707/PPTP-vulnerability-pub.html

Cisco Security Advisory: Cisco IOS PPTP Vulnerability

Revision 1.1

For Public Release 2001 July 12 08:00 (UTC -0800)

Summary

 Point-to-Point Tunneling Protocol (PPTP) allows users to tunnel to an
Internet Protocol (IP) network using a Point-to-Point Protocol (PPP). The
protocol is described in RFC2637. 

 PPTP implementation using Cisco IOS® software releases contains a
vulnerability that will crash a router if it receives a malformed or crafted
PPTP packet. To expose this vulnerability, PPTP must be enabled on the router.
PPTP is disabled by default. No additional special conditions are required. 

 his vulnerability is present in all Cisco IOS releases that support PPTP.
PPTP is supported in the following software releases: 


12.1 train, releases: T, E, EZ, XM, XV, YA, YB, YD and YC 

12.2 train, all releases

No other Cisco product is vulnerable. 

There is no workaround for this vulnerability. 

This advisory is available at  http://www.cisco.com/warp/public/707/PPTP-vulnerability-pub.html. 

Affected Products

 his vulnerability is present in all Cisco IOS releases that support PPTP.
PPTP is supported in the following releases: 


12.1 train, releases: T, E, EZ, XM, XV, YA, YB, YD and YC 

12.2 train, all releases 

To determine if a Cisco product is running an affected IOS, log in to the
device and issue the command show version. Look for the "Internetwork Operating
System Software" or "IOS (tm)" information, which also will have a version
number. Other Cisco devices either will not have the command show version or
will give different output. 

Details

By sending a crafted PPTP packet to port 1723, a control PPTP port, it is
possible to crash the router. This vulnerability does not require special
router configuration. Enabling PPTP is sufficient to expose the vulnerability.
The router will crash after it receives a single packet. 

This vulnerability is documented as Cisco Bug ID CSCdt46181. 

Impact

 By repeatedly exploiting this vulnerability, it is possible to cause
permanent Denial of Service (DoS). This denial is not only of the PPTP
functionality but the whole router will stop functioning. 

Software Versions and Fixes

 Each row of the table describes a release train and the platforms or products
for which it is intended. If a given release train is vulnerable, then the
earliest possible releases that contain the fix and the anticipated date of
availability for each are listed in the "Rebuild," "Interim," and "Maintenance"
columns. A device running a release in the given train that is earlier than the
release in a specific column (less than the earliest fixed release) is known to
be vulnerable. The release should be upgraded at least to the indicated release
or a later version (greater than the earliest fixed release label). 

When selecting a release, keep in mind the following definitions: 

Maintenance 
 Most heavily tested and highly recommended release of any label in a given
row of the table. 

 Rebuild 
 Constructed from the previous maintenance or major release in the same train,
it contains the fix for a specific defect. Although it receives less testing,
it contains only the minimal changes necessary to effect the repair. 

 Interim 
 Built at regular intervals between maintenance releases and receives less
testing. Interims should be selected only if there is no other suitable release
that addresses the vulnerability. Interim images should be upgraded to the next
available maintenance release as soon as possible. Interim releases are not
available via manufacturing, and usually they are not available for customer
download from CCO without prior arrangement with the Cisco TAC. 

 In all cases, customers should exercise caution to be certain the devices to
be upgraded contain sufficient memory and that current hardware and software
configurations will continue to be supported properly by the new release. If
the information is not clear, contact the Cisco TAC for assistance as shown in
the following section. 

 More information on Cisco IOS release names and abbreviations is available at
http://www.cisco.com/warp/public/620/1.html. 



-- 
Dragos Ruiu <dr () dursec com>   dursec.com ltd. / kyx.net - we're from the future 
gpg/pgp key on file at wwwkeys.pgp.net or at http://dursec.com/drkey.asc

_______________________________________________
Snort-users mailing list
Snort-users () lists sourceforge net
Go to this URL to change user options or unsubscribe:
http://lists.sourceforge.net/lists/listinfo/snort-users
Snort-users list archive:
http://www.geocrawler.com/redir-sf.php3?list=snort-users