SharePoint Workflow failed to start suddenly

In one of our SharePoint Farms we recognized, that suddenly some SharePoint Workflows shows a message “Failed to start”. We tried to manually restart them, but the error comes again. After investigation of error logs and workflows in SharePoint Designer we realized that only some of the workflows didn’t work. Those who uses conditions and special tasks belonged to the workflows not working anymore.

One of the error messages was:

“System.CodeDom.CodeBinaryOperatorExpression is not marked as authorized in the application configuration file”

So we tried to republish the workflow. But SharePoint Designer throwed an similiar message, that activities or conditions could not be found. But only at workflows which didn’t run. We could republish working workflows.

After some more research, we found a really good article, which helped in this situation:

“After installing .NET security patches to address CVE-2018-8421, SharePoint workflows stop working (KB 4457916/4457035 and others)”

So the reason was an security patch. After adding the entries into the web.config of SharePoint the Workflows worked again.

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About Karsten Schneider 308 Articles
Consultant for Microsoft 365 Applications with a strong focus in Teams, SharePoint Online, OneDrive for Business as well as PowerPlatform with PowerApps, Flow and PowerBI. I provide Workshops for Governance & Security in Office 365 and Development of Solutions in the area of Collaboration and Teamwork based on Microsoft 365 and Azure Cloud Solutions. In his free time he tries to collect tipps and worthy experience in this blog.

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