Explorer Access Violates When Viewing a File's Properties

• Microsoft Windows NT Workstation version 4.0
• Microsoft Windows NT Server version 4.0

SYMPTOMS

When you use Windows NT Explorer to view the properties of a file, an access violation occurs. If Dr. Watson is installed, it gives the standard AV pop-up error message, for example:

   An application error has occurred and an application error log is being
   generated.

   Explorer.exe
   Exception: access violation (0xc0000005), Address 0x77f64b53

CAUSE

This error can be caused if a file's property set has a corruption. In this case, the thumbnail for the file had an empty Binary Large Object Bitmap (BLOB) stored in the place of a CLIPDATA structure. Because Windows NT Explorer expects the serialized CLIPDATA to have a minimum size of 12 bytes but finds the empty BLOB to have only 8 bytes, it concludes that the discrepancy must be caused by data corruption and exits with the above error. During the exit, Windows NT Explorer cleaned up the allocated *CLIPDATA structure, but in so doing tried to free CLIPDATA.pClipData, which hadn't been allocated at the point of the failure.

The fix now zero initializes the CLIPDATA structure after allocation.

RESOLUTION

To resolve this problem, obtain the hotfix below, or wait for the next service pack.

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 4.0. A supported fix is now available, but is not fully regression tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Product Support Services for more information.