Jet 3.5 Text ISAM Allows Users to Append Lines to System Files

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Article ID: 239105 - View products that this article applies to.
This article was previously published under Q239105
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Novice: Requires knowledge of the user interface on single-user computers.

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SYMPTOMS

The Text ISAM allows you to manipulate text files without checking the file name extension. This creates a potential security risk because it can be used to read or write to a system text file.

NOTE: Until you add the nonstandard text file extension to the HKEY_LOCAL_MACHINE\Software\Microsoft\Jet\3.5\Engines\Text\DisabledExtensions registry key, the error that you will receive during export/import operations using the updated text ISAM will be:
Can't Update. Database or object is read-only.

An error occurred trying to import file.
'<FullPath and Filename>'. The file was not imported.

CAUSE

The Text ISAM is able to modify the contents of text files that are formatted as data tables. This feature makes it easy for you to exchange data on different systems.

RESOLUTION

Install the latest update to the Microsoft Jet database engine. The following registry key is dynamically added when a program loads the Text ISAM. This registry key prevents this type of security risk.
HKEY_LOCAL_MACHINE\Software\Microsoft\Jet\3.5\Engines\Text\DisabledExtensions
For additional information about how to obtain the Microsoft Jet 3.51 update, please click the article number below to view the article in the Microsoft Knowledge Base:
172733 ACC97: Updated Version of Microsoft Jet 3.5 Available on MSL

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

MORE INFORMATION

NOTE: Jet35sp3.exe was updated on October 11, 1999. If you previously installed this update and would like to use the stricter security control provided in the updated MSText35.dll run the installed MSText35.REG file. To run the Mstext35.reg file, locate the file on your system and double-click it.

There could be a possible security risk when someone uses the Text ISAM to modify any of the system text files, such as Autoexec.bat, Config.sys, System.ini, and so on.

After you install the updated version of Jet, you will only be able to use the Text ISAM to update text files with the following extensions:
  • txt
  • csv
  • tab
  • asc
  • htm
  • html
These are the default extensions that are added to the registry key listed in the "Resolution" section. The Value data for the registry key is:
!txt,csv,tab,asc,htm,html
In the first release of Jet 3.5 SP3, you were not be able to use the Text ISAM to update text files with the following extensions:
  • bat
  • cmd
  • ini
  • sys
  • inf
  • vbs
  • js
These are the default extensions that were added to the registry key listed in the "Resolution" section with the first release of Jet 3.5 SP3. The Value data for the registry key was:
bat,cmd,ini,sys,inf,vbs,js
NOTE: The first release of Jet 3.5 SP3 did not provide the use of an exclamation mark (!). When you place an exclamation mark at the beginning of the Value data, you can modify only files with the extensions listed. When you do not place an exclamation mark at the beginning of the Value data, you cannot modify files with the extension listed. NOTE: Microsoft Access users may receive the following error when trying to import a text file that is not one of the enabled extensions:
Can't Update. Database is read-only.
To resolve the error, either rename the file extension to one of the enabled extension types or modify the DisabledExtensions registry key using the methods in this article.

Properties

Article ID: 239105 - Last Review: October 21, 2013 - Revision: 3.1
APPLIES TO
  • Microsoft Access 97 Standard Edition
  • Microsoft Office 97 Professional Edition
  • Microsoft Open Database Connectivity Driver for Access 3.5
Keywords: 
kbnosurvey kbarchive kbbug kbpending KB239105

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