Two vulnerabilities have been reported in Microsoft ISA Server 2000, which can be exploited by malicious people to manipulate contents in the web cache or bypass certain security restrictions.

1) An error in the handling of malformed HTTP requests containing multiple "Content-Length" headers can be exploited to poison the web cache of the ISA server.

Successful exploitation may allow bypassing of content restrictions or cause users' requests to be redirected, but requires that the ISA server has been configured to publish a web server or proxy web content.

2) An error when validating NetBIOS connections can be exploited by malicious people to create a NetBIOS connection with the ISA server via the NetBIOS (all) predefined packet filter.

Successful exploitation requires that the NetBIOS (all) predefined packet filter has been enabled to allow access to local services using the NetBIOS protocol.

A security issue has also been reintroduced by a previous patch, which may result in Basic Credentials being sent over an external HTTP connection even though SSL is required.

Solution
Apply patch.
Further details available to Secunia VIM customers

Provided and/or discovered by
The vendor credits Steve Orrin of Watchfire for reporting the first vulnerability.

The vendor also credits Han Valk for reporting the Basic Credentials issue.

Changelog
Further details available to Secunia VIM customers

Original Advisory
MS05-034 (KB899753):
http://www.microsoft.com/technet/security/bulletin/ms05-034.mspx

Watchfire:
http://www.watchfire.com/resources/HTTP-Request-Smuggling.pdf

Other references
Further details available to Secunia VIM customers

Deep Links
Links available to Secunia VIM customers