CVE-2026-108398: .NET Framework Security Feature Bypass Vulnerability

Overview

Severity

High (CVSS 8.8)

CVSS Vector

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

Category

Security Feature Bypass

Exploit Status

Not Exploited

Exploitation Likelihood

Less Likely

Publicly Disclosed

Yes

Patch Tuesday

2026-Oct

Released

2026-10-13

Description

Untrusted search path in .NET Framework allows an authorized attacker to bypass a security feature locally.

FAQ

What kind of security feature could be bypassed by successfully exploiting this vulnerability? An attacker who successfully exploits this vulnerability could bypass Windows Defender Application Control (WDAC) enforcement. This could lead to the ability to run unauthorized applications on target systems. How could an attacker exploit this vulnerability? An authenticated attacker could place a specially crafted .NET assembly on an affected system and register it for loading by a protected process. Successful exploitation could bypass Windows Defender Application Control restrictions and allow the attacker to execute code within the protected process. User interaction is not required.

Affected Products (24)

Developer Tools

• Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows 10 version 1607
• Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2016
• Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2019
• Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 version 1809
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 version 1809
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 version 21H2
• Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 version 22H2
• Microsoft .NET Framework 3.5 AND 4.8 on Windows Server 2019
• Microsoft .NET Framework 3.5 AND 4.8 on Windows Server 2022
• 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 R2
• Microsoft .NET Framework 4.8 on Windows 10 version 1607
• Microsoft .NET Framework 4.8 on Windows Server 2012
• Microsoft .NET Framework 4.8 on Windows Server 2012 R2
• Microsoft .NET Framework 4.8 on Windows Server 2016
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 version 21H2
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 version 22H2
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 version 24H2
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 version 25H2
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2025
• Microsoft .NET Framework 4.8.1 on Windows 11 version 26H1
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 version 23H2
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2022
• Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 version 26H2

Security Updates (16)

• 5126868
• 5127666
• 5127685
• 5127683
• 5127687
• 5127667
• 5127668
• 5127684
• 5127686
• 5127688
• 5127689
• 5127690
• 5127691
• 5127692
• 5127693
• 5127694

Acknowledgments

James Forshaw with Google Project Zero

Revision History

• 2026-10-13: Information published.