CVE-2026-23666: .NET Framework Denial of Service Vulnerability

Overview

Severity

High (CVSS 7.5)

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C

Category

Denial of Service

Exploit Status

Not Exploited

Exploitation Likelihood

Less Likely

Patch Tuesday

2026-Apr

Released

2026-04-14

Description

Concurrent execution using shared resource with improper synchronization ('race condition') in .NET Framework allows an unauthorized attacker to deny service over a network.

Affected Products (49)

Developer Tools

• Microsoft .NET Framework 4.8 on Windows 10 Version 1607 for 32-bit Systems
• Microsoft .NET Framework 4.8 on Windows 10 Version 1607 for x64-based Systems
• Microsoft .NET Framework 4.8 on Windows Server 2012
• Microsoft .NET Framework 4.8 on Windows Server 2012 (Server Core installation)
• Microsoft .NET Framework 4.8 on Windows Server 2012 R2
• Microsoft .NET Framework 4.8 on Windows Server 2012 R2 (Server Core installation)
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 1809 for 32-bit Systems
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 1809 for x64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 1809 for ARM64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8 on Windows Server 2022
• Microsoft .NET Framework 3.5 AND 4.8 on Windows Server 2022 (Server Core installation)
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 21H2 for 32-bit Systems
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 21H2 for ARM64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 21H2 for x64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 22H2 for x64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 22H2 for ARM64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 22H2 for 32-bit Systems
• Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 Version 1809 for 32-bit Systems
• Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 Version 1809 for x64-based Systems
• Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 Version 1809 for ARM64-based Systems
• Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012
• Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012 (Server Core installation)
• Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012 R2
• Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012 R2 (Server Core installation)
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2022
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2022 (Server Core installation)
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 21H2 for 32-bit Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 21H2 for ARM64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 21H2 for x64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 22H2 for ARM64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 22H2 for x64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 22H2 for x64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 22H2 for ARM64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 22H2 for 32-bit Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 25H2 for ARM systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 25H2 for x64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 23H2 for ARM64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 23H2 for x64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2022, 23H2 Edition (Server Core installation)
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 24H2 for ARM64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 24H2 for x64-based Systems
• Microsoft .NET Framework 3.5 on Windows Server 2012
• Microsoft .NET Framework 3.5 on Windows Server 2012 (Server Core installation)
• Microsoft .NET Framework 3.5 on Windows Server 2012 R2
• Microsoft .NET Framework 3.5 on Windows Server 2012 R2 (Server Core installation)
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2025 (Server Core installation)
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 version 26H1 for x64-based Systems
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2025
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 26H1 for ARM64-based Systems

Security Updates (18)

• 5082411
• 5082403
• 5082404
• 5082414
• 5082427
• 5082426
• 5082413
• 5082400
• 5082402
• 5082425
• 5082419
• 5082424
• 5082417
• 5082418
• 5082420
• 5082398
• 5082406
• 5082421

Acknowledgments

Anonymous

Revision History

• 2026-04-14: Information published.