Malformed Help File Causes Help Utility to Stop Responding

ID: Q231605

The information in this article applies to:

Microsoft Windows NT Workstation versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4
Microsoft Windows NT Server versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4
Microsoft Windows NT Server, Enterprise Edition versions 4.0, 4.0 SP4

SYMPTOMS

A specially-malformed Microsoft Help file may be used to exploit a security vulnerability on a Windows NT-based computer. When a user activates the Windows Help file tool (for example, by pressing the F1 key) this vulnerability may be used to run a program and may cause the Help file tool to stop responding (hang).

CAUSE

The Help tool parses and displays Help information for programs. The Help information is contained in several file types that are generated by the Microsoft Help Compiler program and are stored (by default) in the %SystemRoot%\Help folder. Users have both Read and Write permissions to this folder by default. An unchecked buffer exists in the Help utility, and a Help file that has been carefully modified could be used to run a program on the local computer using a buffer overrun technique. Because the Help Compiler program's output files do not generate the specific malformation at issue here, this vulnerability could not be accidentally exploited.

RESOLUTION

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:

http://www.microsoft.com/Windows/ServicePacks/

Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack

For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://www.microsoft.com/support/supportnet/overview/overview.asp

This hotfix has been posted to the following Internet location as Winhlp-i.exe (x86) and Winhlp-a.exe (Alpha):

ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/nt40/hotfixes-postSP5/winhlp32-fix/

NOTE: This hotfix can be applied to computers running Windows NT 4.0 Service Pack 4 or Windows NT 4.0 Service Pack 5.

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. This problem was first corrected in Windows NT 4.0 Service Pack 6.

MORE INFORMATION

Computers primarily at risk from this vulnerability are workstations, terminal servers, and other computers that allow users to log on interactively and add or modify Help files. Servers generally do not allow normal users to interactively log on. Note that this vulnerability would affect only the local computer; there is no capability to directly attack a remote computer by means of this vulnerability.

For related information on this problem, please visit the Web site at:

http://www.microsoft.com/security/bulletins/MS99-015.asp

For additional security-related information about Microsoft products, please visit the Web site at:

http://www.microsoft.com/security/

Additional query words:

Keywords :
Version : winnt:4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4
Platform : winnt
Issue type : kbbug