Each month, the team at Readiness analyzes the latest Patch Tuesday updates from Microsoft and provides detailed, actionable testing guidance. This guidance is based on assessing a large application portfolio and a comprehensive analysis of the Microsoft patches and their potential impact on Windows platforms and application deployments.
April’s Patch Tuesday release brings broad but non-disruptive changes across the Windows platform. While there are no functional changes reported, this update cycle touches critical components across security, networking, media, and core system services. Here’s what enterprise IT teams and testers need to look out for.
Security & Authentication
Several updates target core identity and authentication components, particularly lsasrv.dll, ci.dll, and skci.dll. These underpin scenarios involving Windows Hello, PIN logins, and certificate services. Even though labeled low-risk, these areas are foundational and demand extra care in testing:
- Windows Defender Application Control (WDAC): Validate AppID tagging and policy updates post-reboot.
- LSASS (Local Security Authority Subsystem Service): Test authentication across AAD, AD, and workgroups. Use tools like runas.exe and confirm no regressions in NTLM, Kerberos, or certificate-based flows.
- BitLocker & VBS Security: Windows Hello and VPN connections should work uninterrupted. Reboot testing is essential to catch potential bootloader integrity issues.
Networking & Remote Access
This release includes updates to multiple RRAS-related DLLs (ipmontr.dll, ipsnap.dll, mprapi.dll), netbt.sys, and tcpip.sys, all of which underpin Windows’ networking stack.
- RRAS & Netsh: Validate remote configuration and scripting scenarios. Commands like netsh interface and MMC snap-ins must execute without issues.
- NetBIOS Controls: Non-admin users in the Network Configuration Operators group should only affect allowed scopes. Test firewall rules and registry protection.
- HTTP.sys & Web Services: Host internal web services and simulate browser-based traffic to confirm consistent response behavior under load.
Remote Desktop & Virtualization
Remote Desktop Protocol (RDP) support remains a high-impact area. Multiple updates to aaedge.dll, mstscax.dll, and rdpcore.dll require validation.
- Remote Desktop Gateway (RDGW): Confirm cross-user connections, session persistence (reconnects, logins), and stability across Windows Server editions.
- Virtualization with VHDs: Validate NTFS volume mount/dismount from VHDs. Create, attach, and manipulate VHD-based virtual disks with file I/O operations.
Media, Graphics, and UI
Multimedia and UI components received several under-the-hood updates. These don’t add features, but any instability here can hurt user experience.
- Graphics Stack: Run screen sharing and capture scenarios. WinUI apps using animation shadows should behave consistently.
- Media Foundation: Playback tests on Blu-ray content with subtitles are a must. Check for regressions in rendering.
- Gaming Tools: Use the Game Bar (Win+G) to test screenshots and recordings during gameplay on Windows 11. Microsoft recommends that you install several (at least three) games to fully test out this graphics stack change. We never had it so good.
File System & Storage
This month’s patches impact how Windows file systems respond to directory change notifications and mount events. Be sure to:
- Simulate NTFS events: Monitor file creation/deletion in Explorer-style interfaces.
- Reboot & Remount: Mount VHDs, perform file operations, then reboot to ensure persistence and data integrity.
Given the large number of security related changes to the Windows platform this month, the Readiness team recommends the following general testing (in addition to the previous recommendations) using both system and user based accounts:
- Basic authentication scenarios using passwords, PIN, and biometrics in a workgroup, AD and AAD environment
- Digital rights management applications (3rd party and Microsoft)
- SMB and IIS access that requires certificate based authentication.
- Ensure your line-of-business applications that rely on HTTPS are still accessible.
When working through these testing scenarios, look for memory leaks and processor spikes in the kernel.
