Environment

• Citrix Virtual Apps and Desktops (CVAD)
• Reported on Citrix VDA 2511 (May impact other versions)
• Windows 11 (24H2 / 25H2)
• October 2026 Security Update (KB5127648)

Caution! Using Registry Editor incorrectly can cause serious problems that might require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.

Under investigation. Microsoft and Citrix engineering teams are jointly analyzing the issue.

Workaround / Mitigation

A validated mitigation has been identified by configuring the following registry setting:

reg add "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" /v TypeOfAdminApprovalMode /t REG_DWORD /d 1 /f

Registry Details:

Key Path:
-HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
Value / Type / Data:
-TypeOfAdminApprovalMode (REG_DWORD) = 1

After applying the registry key and rebooting the system:

• Citrix VDA registration completes successfully.
• Virtual desktops become accessible to users.
• Mitigation was verified across multiple independent test VDIs.

Note: This configuration serves as a temporary workaround while a permanent resolution is being investigated.

Symptoms

After installing the October 2026 Windows security update (KB5127648), Citrix Virtual Desktop sessions fail to launch. Affected machines exhibit the following behavior:

• The Virtual Delivery Agent (VDA) remains stuck in a "Registering" state.
• The Citrix console continuously displays "Trying to re-register".
• Users are unable to launch Citrix virtual desktops.
• Standard RDP connectivity (MSTSC) continues to function normally.
• Uninstalling update KB5127648 restores expected Citrix functionality.

During the registration failure, the Delivery Controller's Broker Service records Event ID 131075 in the Windows Event Log / WCF End-to-End Traces (System.ServiceModel), indicating an authentication negotiation failure when establishing communication with the worker agent.

Event Details