Introduction

In February 2025, Microsoft released security update KB5051987 for Windows Server 2025. Shortly after deployment, administrators reported significant issues with Remote Desktop Protocol (RDP) sessions freezing, leading to operational disruptions. This article delves into the problem's background, technical details, implications, and provides solutions for IT professionals.

Background

Windows Server 2025 and RDP

Windows Server 2025 is a robust platform for enterprise environments, offering enhanced security and performance features. RDP is a critical tool within this ecosystem, enabling remote management and access to server resources.

February 2025 Security Update (KB5051987)

Released on February 11, 2025, KB5051987 aimed to address various security vulnerabilities. However, post-installation, many users experienced RDP sessions freezing shortly after connection, rendering mouse and keyboard inputs unresponsive. This necessitated disconnecting and reconnecting to restore functionality.

Technical Details

Issue Manifestation
  • Symptom: RDP sessions become unresponsive shortly after initiation.
  • Impact: Mouse and keyboard inputs cease to function within the session.
  • Temporary Workaround: Disconnecting and reconnecting the session restores functionality temporarily.
Root Cause Analysis

The freezing issue was linked to changes introduced in the KB5051987 update, affecting the stability of RDP sessions. The exact technical mechanisms remain undisclosed, but the correlation between the update and the issue was evident.

Implications and Impact

Operational Disruptions
  • Productivity Loss: IT administrators faced challenges in managing servers remotely, leading to delays in routine maintenance and troubleshooting.
  • Increased Support Tickets: End-users relying on RDP for remote work reported frequent disruptions, escalating support requests.
Security Concerns
  • Patch Management Dilemma: Organizations had to choose between maintaining security by applying the update and ensuring operational stability by delaying it.
  • Potential Vulnerabilities: Delaying the update could expose systems to unpatched security vulnerabilities.

Solutions and Recommendations

Microsoft's Response

Microsoft acknowledged the issue and released a resolution in the April 2025 cumulative update (KB5055523). Administrators are advised to install this update to resolve the RDP freezing problem.

Immediate Workarounds

For those unable to apply the update immediately, the following workaround was suggested:

  • Disable UDP for RDP:
    • Group Policy:
      • Navigate to INLINECODE0 .
      • Enable the policy "Turn off UDP on client".
    • Registry:
      • Set the INLINECODE1 DWORD value to INLINECODE2 under INLINECODE3 .
Best Practices for IT Administrators
  • Test Updates in Staging Environments: Before deploying updates to production servers, test them in a controlled environment to identify potential issues.
  • Monitor Official Channels: Stay informed through Microsoft's official communications for timely updates and patches.
  • Implement Robust Rollback Procedures: Ensure that rollback plans are in place to revert updates if critical issues arise.

Conclusion

The RDP freezing issue following the February 2025 security update underscores the importance of thorough testing and prompt response to post-update anomalies. By applying the April 2025 cumulative update and adhering to best practices, IT professionals can mitigate such issues and maintain both security and operational efficiency.