Microsoft has released an out-of-band emergency update to resolve a critical issue affecting Remote Desktop connections on Windows client devices.
The problem emerged immediately following the installation of the January 2026 security update, identified as KB5074109. Administrators and users reported widespread credential prompt failures when attempting to sign in via the Windows App, significantly disrupting access to Azure Virtual Desktop and Windows 365 environments.
The original update, released on January 13, 2026, was intended to address routine security vulnerabilities and bugs for systems running specific Windows builds.
However, shortly after deployment, users discovered that they could no longer authenticate successfully when initiating remote sessions. This impacted organizations relying on virtualized desktop infrastructure, as employees were unable to access their cloud-hosted workstations.
Remote Desktop Connection Failures
The technical root cause was traced to a regression in how the Windows App handles credential prompts on specific OS builds (Builds 26200.7623 and 26100.7623).
When users attempted to connect, the authentication interface failed to process credentials correctly, resulting in repeated sign-in errors. This effectively locked users out of remote environments despite entering valid usernames and passwords.
The impact was particularly severe for enterprise environments utilizing Azure Virtual Desktop and Windows 365, where the Windows App serves as the primary gateway for connectivity.
The glitch was isolated to the client-side handling of the connection, meaning the server infrastructure remained functional, but the client devices could not complete the handshake required to establish the session.
Mitigation
Microsoft acknowledged the issue quickly and expedited a resolution. The company has now released a standalone “out-of-band” update, KB5077744, specifically designed to patch the regression introduced by the previous update.
This fix restores normal functionality to the Windows App and ensures that credential prompts behave as expected during Remote Desktop sessions.
System administrators managing affected endpoints are advised to deploy KB5077744 immediately to restore service availability. This update increments the OS build numbers to 26200.7627 and 26100.7627.
Patch Details
| Update Type | KB Number | Release Date | Affected Builds | Fixes |
|---|---|---|---|---|
| Problematic Update | KB5074109 | Jan 13, 2026 | 26200.7623, 26100.7623 | Security fixes (caused RDP failure) |
| Resolution Update | KB5077744 | Jan 17, 2026 | 26200.7627, 26100.7627 | Fixes credential prompt failure |
Affected Platforms
| Platform | Component | Symptom |
|---|---|---|
| Azure Virtual Desktop | Windows App | Credential prompt failure / Sign-in error |
| Windows 365 | Windows App | Credential prompt failure / Sign-in error |
| Windows Client | Remote Desktop | Inability to connect to remote host |
Administrators can download the remediation patch directly from the Microsoft Update Catalog or through their standard update management channels, such as Windows Server Update Services (WSUS) and Microsoft Intune.
Applying this update does not require removing the previous security patch, ensuring that devices remain protected against the vulnerabilities addressed on January 13 while regaining remote connectivity.
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