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AUSCERT External Security Bulletin Redistribution
ESB-2003.0529 -- Cisco Security Notice
Data Leak in UDP Echo Service
01 August 2003
AusCERT Security Bulletin Summary
Publisher: Cisco Systems
Impact: Access Privileged Data
Access Required: Remote
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Data Leak in UDP Echo Service
If the udp-small-servers command is enabled, a Cisco IOS® 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
Workarounds are available to mitigate the effects.
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:
12.1, 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
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.
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