Microsoft IIS 4 Redirect Remote Buffer Overflow Vulnerability



Date Discovered

July 13, 2004


Microsoft IIS 4.0 is reported prone to a buffer overflow vulnerability when handling redirects. It is reported that an attacker may exploit this vulnerability by issuing a large request to an affected IIS Web server. An attacker may exploit this issue to execute arbitrary code in the context of IIS. This could lead to complete compromise of an affected computer.

Technologies Affected

  • Avaya DefinityOne Media Servers
  • Avaya IP600 Media Servers
  • Avaya S3400 Message Application Server
  • Avaya S8100 Media Servers
  • Microsoft IIS 4.0
  • Microsoft IIS 4.0 alpha


Block external access at the network boundary, unless external parties require service.
Unless the Web server is required globally, limit access to only trusted hosts and networks.

Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy network intrusion detection systems to monitor network traffic for signs of anomalous or suspicious activity. This may aid in detection of attacks or malicious activity that may occur as a result of successful exploitation.

Run all software as a nonprivileged user with minimal access rights.
Ensure IIS is running with the least privileges required to successfully operate. This may limit the potential damage that a successful attack may achieve.

Microsoft has released an updated security bulletin (MS04-021) and updates to address this issue for supported operating system versions. The updates listed in MS04-021 require that the updates listed in MS03-018 be installed as a perquisite. Please see the referenced advisories for further information. Avaya has released an advisory that acknowledges this vulnerability for Avaya products. Avaya advise that customers follow the Microsoft recommendations to address this issue. Please see the referenced Avaya advisory at the following location for further details:



This vulnerability was disclosed by the vendor.

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