Critical Issue After September 2026 SharePoint 2019 Updates – Workflows and Web Parts Blocked

Question

Critical Issue After September 2026 SharePoint 2019 Updates – Workflows and Web Parts Blocked

Sai Charan GS 100

Dear Team,

We are currently facing a critical issue in our SharePoint Server 2019 On-Premises production environment after installing the latest SharePoint updates released in September 2026.

The following updates were installed and deployed at the farm level:

Security Update for Microsoft SharePoint Server 2019 Language Pack – KB5002911 (Farm Deployment)
Security Update for Microsoft SharePoint Server 2019 Core – KB5002909 (Farm Deployment)

Following the installation of these updates, we started experiencing issues with several existing workflows and custom Web Parts, which are now being blocked or are no longer functioning as expected. This is having a significant impact on our business operations and day-to-day activities.

Our environment is currently using SharePoint Server 2019 On-Premises, including SharePoint 2010 workflows, which were functioning correctly prior to applying the above updates.

We have already investigated the issue and tried the approach mentioned in the following article:
https://blog.stefan-gossner.com/2026/08/14/are-you-using-sp2010-or-sp2013-workflows-in-your-sharepoint-farms-this-post-is-for-you/

However, the recommended approach did not resolve the issue in our environment, and we continue to experience the problem.

Current Impact

This issue is now critical from a production and business continuity perspective, as multiple existing workflows and Web Parts are affected. These components are required for our regular business processes, and the current behavior is causing significant interruption to our users.

Assistance Requested

We kindly request Microsoft's urgent assistance with the following:

Please help us identify the root cause of the issue and confirm whether it is related to KB5002909 and/or KB5002911.
Please provide a Microsoft-supported solution or workaround that will allow our existing SharePoint 2010 workflows and affected Web Parts to continue functioning normally.
If the behavior is due to a security or compatibility change introduced by these updates, please advise whether there is any supported configuration or alternative approach that can be implemented without compromising the security updates.
If there is currently no available workaround, please confirm whether KB5002909 and/or KB5002911 can be safely uninstalled/rolled back from a SharePoint Server 2019 farm.
If rollback is supported, please provide the recommended Microsoft-supported procedure and prerequisites for uninstalling these updates.
Please also clarify the potential impact of rolling back these updates on our SharePoint 2019 farm, Web Applications, databases, custom solutions, workflows, Web Parts, configurations, and other SharePoint components.
If there is any other recommended approach that would allow us to continue our business operations without interruption while retaining the latest security updates, we would greatly appreciate your guidance.

We understand that the security updates may include important security fixes, and our preference is to retain the updates if a supported workaround or configuration change is available. However, due to the current production impact, we need an immediate and reliable way to restore the affected functionality.

Considering the severity of the production impact, we sincerely request your urgent assistance in investigating and resolving this issue at the earliest possible opportunity.

Thank you for your time and support. We greatly appreciate your assistance and look forward to your guidance on the recommended next steps.

Best Regards,
[Moderator note: Personally Identifiable Information removed]

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Answer 1

Hi Sai,

Thank you for taking the time to share the detailed information regarding the impact you're experiencing after installing the recent SharePoint updates.

Based on the Microsoft documentation for the September 2026 SharePoint security updates, if the issue started after installing the SharePoint update together with the corresponding Windows updates, it may be possible to uninstall the related update package as part of your troubleshooting and recovery process, provided this is done in accordance with your organization's change management and backup procedures.

You can review the update documentation here:

Description of the security update for SharePoint Server Subscription Edition: September 08, 2026

Additionally, if you suspect the issue may have been introduced by a recent Windows Update or by the latest SharePoint security updates, you may consider reporting the issue directly from the affected server through Settings > Windows Update > Report a problem. This allows the relevant Microsoft teams to collect diagnostic information and investigate whether the behavior is related to a recent update or a compatibility change.

Please note that this is a user-to-user forum. While community members and moderators can provide guidance and share best practices, we do not have access to your environment and cannot directly investigate or provide a product fix for update-related issues.

I sincerely appreciate your understanding, and I hope this helps point you toward the quickest resolution path for your environment. If you have any concerns or questions, please let me know. I will be happy to assist further.

Kind regards.