Microsoft has identified an issue with the October 2025 Windows security updates, which is affecting smart card authentication and certificate-based operations on all versions of Windows 10, Windows 11, and Windows Server.
The problem occurs due to a change made to strengthen the Windows Cryptographic Services. Users may experience issues such as inability to sign documents, failures in applications that use certificate-based authentication, or smart cards not being recognized as CSP providers in 32-bit apps.
To fix this issue, users can disable a registry key that is enabled by default in the security update. However, it’s essential to back up the registry before editing it, as any errors could lead to system issues.
The DisableCapiOverrideForRSA registry key needs to be set to 0 to resolve the problem. After making this change, users should restart their computer for the changes to take effect.
Note that this issue is temporary and will be resolved in April 2026, when Microsoft removes the compatibility hold preventing users from upgrading their systems to Windows 11 24H2 via Windows Update.
Microsoft has also fixed other known issues related to Remote Desktop authentication failures on Windows 10 systems and IIS website connectivity issues after installing recent security updates.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-october-security-updates-cause-windows-smart-card-auth-issues