Excel 2016 failing to open .xls files (Crashing/Corrupted) after KB5002903 update

My colleagues and I spent hours troubleshooting a widespread issue yesterday and finally found a working solution! Hope this helps anyone facing the same problem.

(My account is under 24 hours old so I couldn't post to r/sysadmin yet, sharing it here first 😅)

Environment:

• OS: Windows 10 / Windows 11
• Software: Microsoft Excel 2016
• Update: KB5002903 (Released around Aug 11)

Symptoms: After installing the KB5002903 update, Excel 2016 is unable to open .xls files. It either crashes immediately upon opening or throws a "file is corrupted" error message.

Solution / Workaround: Overwriting the updated executable files with previous versions fixes the problem. Here are the steps:

1. Find a source computer that has NOT installed the KB5002903 update yet.
2. Copy these two files from the source computer:
   • excel.exe
   • excelcnv.exe
3. Go to the affected computer and navigate to the Office directory:
   • 64-bit Path: C:\Program Files\Microsoft Office\Office16
4. (Recommended) Back up your original files first, then overwrite/replace both excel.exe and excelcnv.exe with the copied versions.

Result: Tested across multiple machines on Win 10 and Win 11, and Excel 2016 can open .xls files normally again!