Today, we are releasing the July 2020 Cumulative Update Preview for .NET Framework 3.5 and 4.8 on Windows 10, version 2004.

Quality and Reliability

This release contains the following quality and reliability improvements.


– Use FIPS-compliant hashes in ASP.Net telemetry data.

– Addresses an issue where “Unspecified” was not an allowed value in config for the ‘cookieSameSite’ attribute of the forms authentication and session state configuration sections.


– A change in .NET Framework 4.8 regressed certain EnterpriseServices scenarios where an single-thread apartment object may be treated as an multi-thread apartment and lead to a blocking failure. This change now correctly identifies single-thread apartment objects as such and avoids this failure.

– Addresses an issue in assemblies with IBC profile data causing Ngen worker processes to crash and fall back to full native images.

– Addresses rare crashes that could occur during thread abort delivery.


– SqlBulkCopy.WriteToServer can cause transactions to in-memory SQL tables, to fail. The client may see an exception with message “Execution Timeout Expired. The timeout period elapsed prior to completion of the operation or the server is not responding.” SqlBulkCopy.WriteToServer was sending an Attention token (cancellation message) after sending data to Sql Server, causing the server to abort the transaction for in-memory tables.

Net Libraries

– Addresses a memory leak in HttpListener.


– When using a UPN Windows username with the format similar to username@dns.domain in the username property of a NetworkCredential when using NetTcpBinding or NetNamedPipeBinding, WCF would incorrectly split the username and dns.domain placing them into the UserName and Domain properties. This is invalid in some scenarios and would result in failing to authenticate. This fix removes the credential modification when using a UPN username. The modification can be re-enabled by setting the AppSetting “wcf:enableLegacyUpnUsernameFix” to true.


– Addresses an issue when spell-checking is enabled in WPF TextBox or RichTextBox, words like “etc.”, “e.g.” are identified as spelling errors incorrectly.

– Addresses an issue when some Per-Monitor Aware WPF applications that run on .NET 4.8 may occasionally encounter a crash with exceptionSystem.ComponentModel.Win32Exception.

– Addresses an issue where TextBlock reflows (makes different line-breaking decisions) during render and hit-test, vs. during measure. The symptoms include missing text, and FailFast crashes during programmatic text processing.

– Addresses an issue with a render thread failure caused by HostVisual disconnecting its target on the wrong thread.

– Addresses an issue with a hang while scrolling a TreeView whose tree is non-uniform, in the sense thata given node’s children govern subtrees whose sizes are quite different.

– Addresses an issue with a crash that can occur when closing a tooltip that is re-entrantly closed by user code. framework #wpf

.NET Framework July 2020 Cumulative Update Preview for Windows 10, version 2004
1.40 GEEK