Chunked encoding post can consume excessive memory on IIS 4.0 webserver

Overview

Microsoft IIS 4.0, circa March 2000, contained a vulnerability that allowed an intruder to consume unlimited memory on a vulnerable server.

Description

Older versions of IIS 4.0, circa March 2000, contained a vulnerability in the chunked-encoding transfer mechanism that permitted an intruder to allocate unlimited memory on the server. Quoting from Microsoft security bulletin MS00-018:

_IIS 4.0 supports chunked encoding transfers, but does not limit the size of the buffer that can be reserved. This would allow a malicious user to request an extremely large buffer for a POST or PUT operation, but never actually send data, thereby blocking memory on the server that had been allocated to the session. _

This would not permit an intruder to execute code.

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Impact

Intruders can interrupt the ordinary operation of a vulnerable IIS 4.0 server, potentially preventing it from responding to legitimate requests. Additionally, an intruder may be able to degrade the overall performance of other process on the machine.

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Solution

Apply a patch as described in MS00-018.

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Vendor Information

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Updated: June 13, 2002

Status

Affected

Vendor Statement

See <http://www.microsoft.com/technet/security/bulletin/ms00-018.asp&gt;

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%2325716 Feedback>).

CVSS Metrics

Group	Score	Vector
Base
Temporal
Environmental

References

• <http://www.microsoft.com/technet/security/bulletin/ms00-018.asp&gt;
• <http://www.microsoft.com/technet/security/bulletin/fq00-018.asp&gt;
• <http://www.microsoft.com/technet/support/kb.asp?ID=252693&gt;
• <http://www.ietf.org/rfc/rfc2616.txt&gt;
• <http://online.securityfocus.com/bid/1066&gt;

Acknowledgements

Thanks to Petteri Stenius for reporting this vulnerability.

This document was written by Shawn V Hernan based on information provided by Microsoft in MS00-018.

Other Information

CVE IDs:	CVE-2000-0226
Severity Metric:	2.62 Date Public: