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Nasty Microsoft Windows Shell Shortcut Parsing Vulnerability Zero Day Found

By July 19, 2010Security


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Here we go again.  Someone has found a nasty way to exploit your Windows machine.  The vulnerability is currently being exploited by W32.Temphid malware.  The issue seems to be in the way that windows parses .lnk shortcut files.  Here is M$’s take on it:

“The vulnerability exists because Windows incorrectly parses shortcuts in such a way that malicious code may be executed when the user clicks the displayed icon of a specially crafted shortcut. This vulnerability is most likely to be exploited through removable drives. For systems that have AutoPlay disabled, customers would need to manually browse to the root folder of the removable disk in order for the vulnerability to be exploited. For Windows 7 systems, AutoPlay functionality for removable disks is automatically disabled.”

There is no current patch.

You can, however, disable displaying icons for link files, and kill this potential exploit.  via US-Cert:

Note Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. For information about how to edit the registry, view the “Changing Keys And Values” Help topic in Registry Editor (Regedit.exe) or view the “Add and Delete Information in the Registry” and “Edit Registry Data” Help topics in Regedt32.exe.

1. Click Start, click Run, type Regedit in the Open box, and then click OK
2. Locate and then click the following registry key:
HKEY_CLASSES_ROOT\lnkfile\shellex\IconHandler
3. Click the File menu and select Export
4. In the Export Registry File dialog box, enter LNK_Icon_Backup.reg and click Save
Note This will create a backup of this registry key in the My Documents folder by default
5. Select the value (Default) on the right hand window in the Registy Editor. Press Enter to edit the value of the key. Remove the value, so that the value is blank, and press Enter.
6. Restart explorer.exe or restart the computer.



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