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This is not a Cisco security advisory.

There is a vulnerability in how Cisco routers are handling CDP.
By sending a large amount of CDP neighbor announcements it is
possible to consume all available router's memory. That will cause
a crash or some other abnormal behavior. This vulnerability is
assigned a Cisco bug ID CSCdu09909. You can see details of it
if you have a valid CCO account. This vulnerability was
discovered by fxphenoelit.de

In order to trigger this vulnerability an attacker must be on the same
segment as the target router. This vulnerability can not be exploited
over the Internet unless an attacker has a helper program already
planted on the internal network.

The workaround for this vulnerability is to disable CDP. In order to
disable CDP for the whole router execute the following global command:

  Router# configure terminal
  Enter configuration commands, one per line. End with CNTL/Z.
  Router(config)# no cdp run

Alternatively, CDP can be disabled on a particular interface. This
can be done using the following commands:

  Router# configure terminal
  Enter configuration commands, one per line. End with CNTL/Z.
  Router(config)# interface Ethernet0
  Router(config-if)# no cdp enable

In this particular case we advise all customers to disable CDP for
the whole router.

This vulnerability has ben fixed in the following interim images:

12.2(3.6)B
12.2(4.1)S
12.2(3.6)PB
12.2(3.6)T
12.1(10.1)
12.2(3.6)

All higher IOS releases should contain this fix.

Please note that interim images are 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,
and 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.

We would like to thank Phenoelit on his co-operation on this issue.

Gaus

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==============
Damir Rajnovic <psirtcisco.com>, PSIRT Incident Manager, Cisco Systems
<http://www.cisco.com/warp/public/707/sec_incident_response.shtml>
Phone: +44 7715 546 033
4 The Square, Stockley Park, Uxbridge, MIDDLESEX UB11 1BN, GB
==============
There is no insolvable problems. Question remains: can you
accept the solution?

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