Microsoft ISA Server HTTP/HTTPS Service Basic Auth Information Disclosure Vulnerability



Date Discovered

June 14, 2005


Microsoft Internet Security and Acceleration (ISA) server is prone to an information disclosure vulnerability. Reports indicate that the issue manifests when an ISA server is publishing a Web service that has Basic authentication enabled, but the Web publishing rules that process the request are configured as 'SSL required'. An attacker that has the ability to intercept network communications between the ISA server and a client may leverage this issue to obtain Web site authentication credentials.

Technologies Affected

  • Microsoft ISA Server 2000
  • Microsoft ISA Server 2000 Enterprise Edition SP1
  • Microsoft ISA Server 2000 Enterprise Edition SP2
  • Microsoft ISA Server 2000 Enterprise Edition
  • Microsoft ISA Server 2000 FP1
  • Microsoft ISA Server 2000 SP1
  • Microsoft ISA Server 2000 SP2


Permit privileged access for trusted individuals only.
Grant access to local networks for trusted and fully accountable users only.

Modify default configuration files to disable any unwanted behavior.
Configure Web services to employ only HTTPS (SSL) protocol for all communications.

Microsoft has released a fix to address this issue.



Discovery of this issue is credited to Han Valk.

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