Microsoft Internet Information Server (IIS) Web Server Discloses ASP Source Code When Installed on FAT-based Filesystem
SecurityTracker Alert ID: 1001818|
SecurityTracker URL: http://securitytracker.com/id/1001818
(Links to External Site)
Date: Jun 22 2001
Disclosure of user information|
Vendor Confirmed: Yes Exploit Included: Yes |
Version(s): Windows NT4 + IIS4 + sp3 (on FAT), Windows 2000 Server (on FAT), Windows 2000 Server + sp2 (on FAT)|
VIGILANTe reported a vulnerability with Microsoft's IIS web server when installed on a FAT filesystem that allows a remote user to obtain Active Server Pages (ASP) source code from the server.|
IIS reportedly determines if a file is an ASP script or not by the .asp extension. If a remote user prepares an HTTP request using Unicode encoding, the asp extension may not be recognized by IIS on FAT filesystems and the ASP code will be returned as source code rather than executed.
The vendor notes that FAT (as opposed to NTFS) does not provide any file security mechanisms and is not appropriate for use as a production web server.
IIS on systems using NTFS volumes is not affected.
A remote user can obtain ASP source code from the web server.|
No vendor solution was available at the time of this entry. The report recommends as a workaround to convert the file system to NTFS and to consider removing reading access right for the IUSR_<hostname> from ASP scripts (only giving IUSR_<hostname> execute rights).|
Vendor URL: www.microsoft.com/technet/security/ (Links to External Site)
Access control error, Input validation error|
|Underlying OS: Windows (NT), Windows (2000)|
Source Message Contents
Subject: [VIGILANTE-2001001] ASP source code retrieved with Unicode extens|
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ASP source code retrieved with Unicode extension
Windows NT4 + IIS4 + sp3 (on FAT)
Windows 2000 Server (on FAT)
Windows 2000 Server + sp2 (on FAT)
Systems not affected:
Windows NT4 + IIS4 + sp3 (on NTFS)
Windows 2000 Server (on NTFS)
Windows 2000 Server + sp2 (on NTFS)
Active Server Pages (ASP) are web scripts that are executed on
the Internet Information Server (IIS) and the result is send to
the user. IIS determines if a file is an ASP script or not by
the .asp extension.
With Unicode there are many ways the asp extension can be
encoded. On FAT file systems some of them will not be
recognized as an ASP script by IIS and executed on the server
but instead IIS will disclouse the source code of the script.
Microsoft contacted 2001-05-28 and responded the same day:
"The Microsoft Security Response Center has investigated the
report, but we note that the problem as reported would only
affect an IIS server that has been configured to use a FAT
volume. However, by design, FAT doesn't provide a security
mechanism, and it's never an appropriate file system to use on
a production web server. Instead, as discussed in Microsoft's
best practices guides and security checklists
production servers should always use NTFS volumes. The reported
problem does not affect systems using NTFS".
A test-case to detect this vulnerability was added to
SecureScan NX on June 22, 2001
As a workaround convert the file system to NTFS. And consider
removing reading access right for the IUSR_<hostname> from ASP
scripts (only giving IUSR_<hostname> execute rights)
In general follow Microsoft's Security Best Practices:
Internet Information Server 4.0 Security Checklist:
or Secure Internet Information Services 5 Checklist:
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