Excel COM instability after KB5060999 installation (Heap corruption issue)

Question

Excel COM instability after KB5060999 installation (Heap corruption issue)

Toru-san 65

Hi Everyone,

Environment:

OS: Windows 11 Enterprise 23H2 (Build 22621.5262)

Excel Version: 16.0.5500.1000 (Office 2016)

Automation Tool: WinActor Ver7.4.4 (VBScript-based)

Issue Summary: After installing KB5060999, Excel COM operations became unstable, causing heap corruption during automated file conversion from HTML-based .xls to .xlsx.

Crash Details:

Application: EXCEL.EXE

Version: 16.0.5500.1000

Fault Module: StackHash_cf51

Exception Code: c0000374 (Heap corruption)

Fault Offset: PCH_D1_FROM_ntdll+0x000773BC

OS Version: 10.0.22621.5262

Technical Context:

The issue began after the April 8, 2025 Windows Updates (KB5055518 / KB5055528).

The automation script uses Excel COM via VBScript in WinActor.

Excel 2024 may offer a workaround using ActiveX instead of COM, but is currently unavailable for testing.

We plan to check the July 2025 Windows Update for any changes or improvements related to COM stability.

Request: Please confirm whether KB5060999 or any upcoming updates include changes affecting Excel COM behavior or heap management. Any guidance or workaround would be appreciated.

Kind Regards,

Toru

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Answer 1

Tammy-Ng 625 Microsoft External Staff Moderator

Dear Toru-san

Thank you for posting your question in the Microsoft Q&A forum.
Based on the information you provided, it appears you're experiencing Excel COM instability after installing update KB5060999. I'm sorry to hear about the issue you're facing.

According to my research, Microsoft has released a newer update on June 26, 2025: KB5060826 – OS Builds 22621.5549 and 22631.5549 (Preview)

You may try uninstalling KB5060999 and then installing this newer update to see if it resolves the issue

You can find the update details here: June 26, 2025—KB5060826 (OS Builds 22621.5549 and 22631.5549) Preview - Microsoft Support

After updating, please try your Excel automation again. If any new errors occur or the issue persists, feel free to reply, I’m here and ready to assist you further.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Toru-san 65 Reputation points

2025-07-04T00:49:43.9833333+00:00

Subject: Interim Update on KB5060826 / KB5060999 Validation

Dear @Tammy-Ng

Thank you for your continued support.

We are currently conducting validation related to KB5060826 and KB5060999. Below is a summary of our findings so far:

Installing KB5060826 triggers the installation of KB5060999.

KB5060999 is visible via Get-HotFix, while KB5060826 is not.

Using DISM /online /get-packages, we confirmed that the package corresponding to KB5060826 (Package_for_RollupFix~...5472.1.10) is installed.

The HTML-to-Excel conversion script is functioning correctly.

We are now performing multiple test runs using the previously developed script. If no issues arise, we plan to proceed with testing in the production environment.

We will provide a formal update once further progress has been made.

Thank you again for your cooperation and understanding.

Kind regards,

Toru
Tammy-Ng 625 Reputation points Microsoft External Staff Moderator

2025-07-07T07:28:35.3766667+00:00

Dear Toru-san,

Thank you for responding.
We're truly glad to hear that the troubleshooting steps are working well on your end. We also sincerely appreciate you taking the time to share your resolution to Excel COM instability after KB5060999 installation

If my initial answer has been even partially helpful, please consider marking it as “Accepted Answer” so others facing similar issues can find it more easily.
Toru-san 65 Reputation points

2025-07-08T01:37:57.7733333+00:00

Subject: Update on KB5060826/KB5060999 Validation – Issue Confirmed in Production

Dear @Tammy-Ng ,

Thank you again for your continued support.

Following our previous validation efforts regarding KB5060826 and KB5060999, we would like to provide an important update.

While our initial testing in the controlled environment showed stable behavior — including successful execution of the HTML-to-Excel conversion script — we have now proceeded to test in the production environment. Unfortunately, we have observed that the issue persists under production conditions.

Specifically, Excel COM operations are still exhibiting instability, including heap corruption errors, despite the presence of KB5060826. This discrepancy between test and production environments is concerning, and we are currently investigating potential environmental factors that may be contributing to the issue.

We wanted to ensure you are aware of this development, as it may impact the timeline for resolution. We will continue to monitor and analyze the behavior and will share further findings as they become available.

Thank you again for your cooperation and understanding.

Kind regards,

Toru
Toru-san 65 Reputation points

2025-07-08T23:05:16.15+00:00

Dear @Tammy-Ng ,

Thank you for your continued support.

The problem is not yet solved, but we are getting closer to it, so I will click “Accepted Answer”.

Thank you for your cooperation this time.

Kind regards,

Toru

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Excel COM instability after KB5060999 installation (Heap corruption issue)

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