[NEWS] Cisco Found To Contain a NTP Related Vulnerability

From: support@securiteam.com
Date: 05/08/02 

From: support@securiteam.com
To: list@securiteam.com
Date: Wed,  8 May 2002 23:48:30 +0200 (CEST)

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  Cisco Found To Contain a NTP Related Vulnerability
------------------------------------------------------------------------

SUMMARY

Network Time Protocol (NTP) is used to synchronize time on multiple
devices. A vulnerability has been discovered in the NTP daemon query
processing functionality. This vulnerability has been publicly announced.

The following products are identified as affected by this vulnerability:
 * All releases of Cisco IOS software
 * Media Gateway Controller (MGC) and related products
 * BTS 10200
 * Cisco IP Manager

Other Cisco software applications may run on Solaris platforms and where
those products have not specifically been identified, customers should
install security patches regularly in accordance with their normal
maintenance procedures.

Cisco is continuing to research this issue in other products that may be
affected. Unless explicitly stated otherwise, all other products are
considered to be not affected.

The workarounds for this vulnerability are described in the Workarounds
section.

DETAILS

Affected Products:
The following products are affected:

 * All releases of Cisco IOS software
 * Media Gateway Controller (MGC) and related products, they encompass the
following products:
   * SC2200
   * Cisco Virtual Switch Controller (VSC3000)
   * Cisco PGW2200 Public Switched Telephone Network (PSTN) Gateway
   * Cisco Billing and Management Server (BAMS)
   * Cisco Voice Services Provisioning Tool (VSPT)
 * BTS 10200
 * Cisco IP Manager

Other Cisco software applications may run on Solaris platforms and where
those products have not specifically been identified, customers should
install security patches regularly in accordance with their normal
maintenance procedures.

Cisco is continuing to research this issue in other products that may be
affected. Unless explicitly stated otherwise, all other products are
considered to be not affected.

Details:
By sending a crafted NTP query packet it is possible to trigger a buffer
overflow in the NTP daemon. This vulnerability can be exploited remotely.
The successful exploitation may cause arbitrary code to be executed on the
target machine. Such exploitation, if it is possible at all, would require
significant engineering skill and a thorough knowledge of the internal
operation of Cisco IOS software or SUN Solaris operating system.

To the best of our knowledge this vulnerability cannot cause arbitrary
code to be executed on Cisco IOS and SUN Solaris.

The vulnerability is present regardless of the role played by the device.
The device may be an NTP server or client and it will still be vulnerable.

For IOS, this vulnerability is documented as Cisco Bug ID CSCdt93866.

The main repository of NTP software and all other information regarding
NTP, can be found at <http://www.eecis.udel.edu/~ntp/>
http://www.eecis.udel.edu/~ntp/.

Impact:
The successful exploitation may cause arbitrary code to be executed on the
target machine. More often, an attempt to exploit this vulnerability will
result in a daemon or device crash.

Software Versions and Fixes
A listing (A table) of available software versions, and their
corresponding patches is available at:
 <http://www.cisco.com/warp/public/707/NTP-pub.shtml#Software>
http://www.cisco.com/warp/public/707/NTP-pub.shtml#Software

Obtaining Fixed Software:
Cisco is offering free software upgrades to remedy this vulnerability for
all affected customers. Customers may only install and expect support for
the feature sets they have purchased.

Customers with service contracts should obtain upgraded software through
their regular update channels to any software release containing the
feature sets they have purchased. For most customers, this means that
upgrades should be obtained through the Software Center on Cisco's
worldwide website at <http://www.cisco.com> http://www.cisco.com.

Customers whose Cisco products are provided or maintained through prior or
existing agreement with third-party support organizations such as Cisco
Partners, authorized resellers, or service providers should contact that
support organization for assistance with the upgrade, which should be free
of charge.

Customers who purchased directly from Cisco but who do not hold a Cisco
service contract, and customers who purchase through third party vendors
but are unsuccessful at obtaining fixed software through their point of
sale, should obtain fixed software by contacting the Cisco Technical
Assistance Center (TAC). In those cases, customers may only upgrade to a
later version of the same release as indicated by the applicable row in
the Software Versions and Fixes table.

Cisco TAC contacts are as follows:
 * +1 800 553 2447 (toll-free from within North America)
 * +1 408 526 7209 (toll call from anywhere in the world)
 * e-mail: tac@cisco.com

See <http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml>
http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for additional
TAC contact information, including special localized telephone numbers and
instructions and e-mail addresses for use in various languages.

Please have your product serial number available and give the URL of this
notice as evidence of your entitlement to a free upgrade. Free upgrades
for non-contract customers must be requested through the TAC.

Please do not contact either "psirt@cisco.com" or
"security-alert@cisco.com" for software upgrades.

Workarounds:
Cisco IOS
There are a few methods available to lower the exposure. You can combine
these methods or use them individually.

 * Prevent IOS from processing NTP queries at all. No other NTP function
is affected by this. This can be accomplished by adding the following
statement into the configuration:
   ntp access-group serve-only

 * Use NTP with authentication. You must enable this feature on all
participating peers and servers. You can enable it in IOS as follows:
   ntp authentication-key 20 md5 your_NTP_key
   ntp authenticate
   ntp trusted-key 20

Note: The key must be the same on all participating peers and servers.

 * It is possible to mitigate the exposure by using ACLs and dropping all
NTP packets that are not from the legitimate servers. This can be
accomplished as follows:

   access-list 10 permit 1.2.3.4
   access-list 10 permit 5.6.7.8
   access-list 10 deny any any
   !
   ntp access-group peer 10

In the above example, 1.2.3.4 and 5.6.7.8 are addresses of peers or
servers from which NTP packets will be accepted.

 * Additionally, if you are not using NTP servers external from your
network, you can drop all NTP packets on the network boundary. This can be
done by the ACL as follows:

   access-list 101 deny udp any any eq ntp

For more detailed information regarding individual commands and additional
examples, please refer to the following documentation:
 
<http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/fun_c/fcprt3/fcd303.htm> http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/fun_c/fcprt3/fcd303.htm
 <http://www.cisco.com/public/cons/isp/essentials/>
http://www.cisco.com/public/cons/isp/essentials/
 
MGC and Related Products
Cisco IP Manager
BTS 10200
 
Although the workaround was posted on the Bugtraq list we recommend
installing the patch provided.
 
The users must follow the installation instructions that are part of the
patch.

ADDITIONAL INFORMATION

The information has been provided by <mailto:psirt@cisco.com> Cisco
Systems Product Security Incident Response Team.

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