Trending Issue: SharePoint 2010 workflows fail after June 2026 CU
We have received multiple reports indicating that SharePoint 2010–style workflows are failing after installing the June 2026 Cumulative Update (CU). Symptoms The issue is typically reflected in the ULS logs with entries similar to the following: w3wp.exe (0xXXXX) SharePoint Foundation Legacy Workflow Infrastructure 4letu High Block the namespace: clr-namespace:System.CodeDom;Assembly=System, Version=4.0.0.0, […]
