Security Alert for XP users

The UPLDDRVINFO.HTM  Vulnerability

This vulnerability allows the files contained in any specified directory on your system to be deleted if you click on a specially formed URL. This URL could appear anywhere: sent in malicious e-Mail, in a chat room, in a newsgroup posting, on a malicious web page, or even execute when your computer merely visits a malicious web page.

MS Tracking ID: [MSRC 1198dg]
Date Reported: 25/06/02
Date Published: 15/08/02
Vendor: Microsoft
Impact: Delete files through CSS condition in Help Center
Resolution: To be fixed in XP SP1
Tested Applications: IE6 + all service packs (to date of publishing)
Windows XP + all patches (to date of publishing)
Help Center (HelpCtr.exe v5.1.2600.0)


Information on the 'Help and Support Center' may be obtained from MSDN at; health/help_and_support_center.asp

Quoting from the above URL;
"Help and Support Center is the unified Help introduced by Windows XP. It is an exapanded version of the Help Center application (introduced in Windows Millenium Editon), providing a wider breadth of content and more features to access that content."

The application also registers the pluggable protocol "hcp://", which may be used to launch the help center from a web site. It is also used for navigation within the center itself. The path and file specified in an URL when using the hcp protocol may specify a file to open relative from the HELPCTR directory. ie. The URL "hcp://system/sysinfo/msinfo.htm" will launch the Help Center and open the file "%windir%\PCHEALTH\HELPCTR\System\sysinfo\msinfo.htm". There are various
restrictions and exceptions, but this is the general idea.

It is important to note that the Help Center will host the page with elevated priviliges, allowing the page to script arbitrary controls with no prompts presented to the user.


The file (32,463 bytes);

Appears to be intended for use by the Help Center to upload hardware/driver information collected on the local machine for use in troubleshooting hardware issues. It also contains the fraction of script;

var oFSO = new ActiveXObject ( "Scripting.FileSystemObject" );
oFSO.DeleteFile( sFile );

Where 'sFile' is derived from the URL. The help center will load the uplddrvinfo.htm file and render it with higher privileges, allowing such script to run without prompts

By using the 'hcp:' protocol, its possible to launch this from a link. The filename can also include wild cards. Thus, the following link will delete all files in the 'C:\windows\' directory when the launched window is closed. (normal file permissions still apply as usual). Sub-directories are not deleted.



Microsoft have noted they intend to roll the fix into SP1 for XP. I informed Microsoft I would be publishing this advisory in mid August during correspondance (late June) and received no objections.

Temporary solutions may be;

+ delete/move the uplddrvinfo.htm file
+ edit the script of uplddrvinfo.htm to remove the offending code
+ unregister the hcp protocol handler

Ironically, the following 'exploit' may also be used as a 'patch' for users running as admin with Windows installed in C:\windows\.

!NOTE: This may delete the 'uplddrvinfo.htm' file.