AUSCERT External Security Bulletin Redistribution

                  ESB-2003.0529 -- Cisco Security Notice
                       Data Leak in UDP Echo Service
                              01 August 2003


        AusCERT Security Bulletin Summary

Product:                IOS
Publisher:              Cisco Systems
Impact:                 Access Privileged Data
Access Required:        Remote

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Hash: SHA1

Data Leak in UDP Echo Service

Revision 1.0


If the udp-small-servers command is enabled, a Cisco IOSĀ® software device may
reply to malformed udp echo packets with some of the contents stored in a
router's memory. By repeatedly sending malformed udp echo packets and capturing
the replies, an attacker can obtain portions of the data that is stored in a
router's memory.

Workarounds are available to mitigate the effects.

Fixed Software

This vulnerability has been fixed by the Cisco Bug ID CSCdk77834. Below are the
first Cisco IOS software releases that are not affected by this vulnerability:

  * 12.0(3.2)
  * 12.0(3.3)S
  * 12.0(3.4)T
  * 12.0(3.6)W5(9.0.5)
12.1, 12.2, and 12.3-based images are not affected.


The workaround is to disable udp-small-services. The syntax for this command on
routers and switches running Cisco IOS software is as follows:

    no service udp-small-servers

The udp-small-servers command is disabled by default since Cisco IOS Software
Release 11.2(1).

It is always recommended to disable unnecessary services on routers and
switches. Refer to Improving Security on Cisco Routers
(http://www.cisco.com/warp/public/707/21.html#possibly_unnecessary) for more 
information on improving router security.

Version: GnuPG v1.2.1 (GNU/Linux)


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