full-disclosure - Potential denial of service bug in Cisco Pix Firewall IOS resolve d in 6.3.(3)105

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From: amilabs at optonline.net (amilabs)
Subject: Potential denial of service bug in Cisco Pix
 Firewall IOS resolve d in 6.3.(3)105

Thanks for the heads up. I have had that problem with nat since 6.1. I
have a pix 501 and it always did this every now and then. So, I would do
a reset or clear xlate to resolve the problem. It seemed to be an ios
issue and not a dos attack issue. I use it for vpn access. It mostly
happens when I am leaving my local network going through the pix and out
onto the cable net. 

Thanks for the tip

www.amilabs.com

-----Original Message-----
From: full-disclosure-admin@...ts.netsys.com
[mailto:full-disclosure-admin@...ts.netsys.com] On Behalf Of
John.Airey@...b.org.uk
Sent: Monday, January 05, 2004 9:55 AM
To: full-disclosure@...ts.netsys.com
Subject: [Full-Disclosure] Potential denial of service bug in Cisco Pix
Firewall IOS resolve d in 6.3.(3)105

Brief Description
-----------------

Users of Cisco Pix Firewalls may discover that their pool of NAT'ted IP
addresses is running out, and that a reboot, reload or "clear xlate" on
the firewall clears the problem.

Details
-------

The problem is caused by the Firewall being swamped by incoming ICMP
packets on the global pool IP addresses. If these are not intercepted by
a router beforehand, the incoming echo requests (that are emanating from
Nachi/Welchia worm infected machines) are preventing the release of the
address translation. ie, the Pix is detecting the blocked traffic as
indication that the translation is still in use.

Permanent fix
-------------

I have been informed by Cisco that this is resolved in 6.3(3)105. The
relevant case ID is CSCec 47609 detailed at 
www.cisco.com/cgi-bin/Support/Bugtool/onebug.pl?bugid=CSCec47609 and
referenced at
www.cisco.com/en/US/products/sw/voicesw/ps556/products_tech_note09186a00
801b
143a.shtml

This is probably also fixed in later IOS versions. 

- 
John Airey, BSc (Jt Hons), CNA, RHCE
Internet systems support officer, ITCSD, Royal National Institute of the
Blind, Bakewell Road, Peterborough PE2 6XU,
Tel.: +44 (0) 1733 375299 Fax: +44 (0) 1733 370848
John.Airey@...b.org.uk 

Even if you win the rat race, that will still only make you a rat.

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