Vulnerability Note VU#25716

Chunked encoding post can consume excessive memory on IIS 4.0 webserver

Original Release date: 13 Jun 2002 | Last revised: 13 Jun 2002


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


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.


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.


Apply a patch as described in MS00-018.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
Microsoft CorporationAffected-13 Jun 2002
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



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
  • Date Public: 20 Mar 2000
  • Date First Published: 13 Jun 2002
  • Date Last Updated: 13 Jun 2002
  • Severity Metric: 2.62
  • Document Revision: 3


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