CVE-2026-34344Important
Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
Assessment
Access of resource using incompatible type ('type confusion') in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
- Severity
- Important
- CVSS base score
- 7.8CVSS:3.1/
AV:L/ AC:L/ PR:L/ UI:N/ S:U/ C:H/ I:H/ A:H/ E:U/ RL:O/ RC:C - Impact
- Elevation of Privilege
- EPSS, next 30 days
- 0.3%Higher than 24.1% of scored CVEs · FIRST model run 29 Sep 2026 · about EPSS
- Public exploit code
- No Nuclei template lists it
- Exploitability
- Exploitation Less Likely
- Publicly disclosed
- No
- Customer action
- Required: apply the update
- Component
- Windows Ancillary Function Driver for WinSock
- Weakness
- CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')
- Issued by
- Microsoft
- Published
- 12 May 2026 · May 2026
- Last revised
- 12 May 2026
Updates that fix it
16 KBs| KB | Type | Restart | Applies to | Other CVEs |
|---|---|---|---|---|
| KB5087420 | Security Update | Required | Windows 11 Version 23H2 for ARM64-based Systems | All CVEs in KB5087420 |
| KB5087423 | Security Hotpatch Update | Required | Windows Server 2025, Windows Server 2025 (Server Core installation) | All CVEs in KB5087423 |
| KB5087424 | Security Hotpatch Update | Required | Windows Server 2022, Windows Server 2022 (Server Core installation) | All CVEs in KB5087424 |
| KB5087470 | Monthly Rollup | Required | Windows Server 2012, Windows Server 2012 (Server Core installation) | All CVEs in KB5087470 |
| KB5087471 | Monthly Rollup | Required | Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation) | All CVEs in KB5087471 |
| KB5087537 | Security Update | Required | Windows 10 Version 1607 for 32-bit Systems, Windows 10 Version 1607 for x64-based Systems, Windows Server 2016 and 1 more | All CVEs in KB5087537 |
| KB5087538 | Security Update | Required | Windows 10 Version 1809 for 32-bit Systems, Windows 10 Version 1809 for x64-based Systems, Windows Server 2019 and 1 more | All CVEs in KB5087538 |
| KB5087539 | Security Update | Required | Windows Server 2025, Windows Server 2025 (Server Core installation) | All CVEs in KB5087539 |
| KB5087541 | Security Update | Required | Windows Server 2022, 23H2 Edition (Server Core installation) | All CVEs in KB5087541 |
| KB5087544 | Security Update | Required | Windows 10 Version 21H2 for 32-bit Systems, Windows 10 Version 21H2 for ARM64-based Systems, Windows 10 Version 21H2 for x64-based Systems | All CVEs in KB5087544 |
| KB5087545 | Security Update | Required | Windows Server 2022, Windows Server 2022 (Server Core installation) | All CVEs in KB5087545 |
| KB5089466 | Security Hotpatch Update | Required | Windows 11 Version 24H2 for ARM64-based Systems, Windows 11 Version 24H2 for x64-based Systems, Windows 11 Version 25H2 for ARM64-based Systems and 1 more | All CVEs in KB5089466 |
| KB5089548 | Security Update | Required | Windows 11 Version 26H1 for ARM64-based Systems, Windows 11 version 26H1 for x64-based Systems | All CVEs in KB5089548 |
| KB5089549 | Security Update | Required | Windows 11 Version 24H2 for ARM64-based Systems, Windows 11 Version 24H2 for x64-based Systems, Windows 11 Version 25H2 for ARM64-based Systems and 1 more | All CVEs in KB5089549 |
| KB5093998 | Security Update | Required | Windows 11 Version 23H2 for x64-based Systems | All CVEs in KB5093998 |
| KB5094127 | Security Update | Required | Windows 10 Version 22H2 for 32-bit Systems, Windows 10 Version 22H2 for ARM64-based Systems, Windows 10 Version 22H2 for x64-based Systems | All CVEs in KB5094127 |
Affected products
ESU, Windows31 affected products
- Windows 10 Version 1607 for 32-bit Systems
- Windows 10 Version 1607 for x64-based Systems
- Windows 10 Version 1809 for 32-bit Systems
- Windows 10 Version 1809 for x64-based Systems
- Windows 10 Version 21H2 for 32-bit Systems
- Windows 10 Version 21H2 for ARM64-based Systems
- Windows 10 Version 21H2 for x64-based Systems
- Windows 10 Version 22H2 for 32-bit Systems
- Windows 10 Version 22H2 for ARM64-based Systems
- Windows 10 Version 22H2 for x64-based Systems
- Windows 11 Version 23H2 for ARM64-based Systems
- Windows 11 Version 23H2 for x64-based Systems
- Windows 11 Version 24H2 for ARM64-based Systems
- Windows 11 Version 24H2 for x64-based Systems
- Windows 11 Version 25H2 for ARM64-based Systems
- Windows 11 Version 25H2 for x64-based Systems
- Windows 11 Version 26H1 for ARM64-based Systems
- Windows 11 version 26H1 for x64-based Systems
- Windows Server 2012
- Windows Server 2012 (Server Core installation)
- Windows Server 2012 R2
- Windows Server 2012 R2 (Server Core installation)
- Windows Server 2016
- Windows Server 2016 (Server Core installation)
- Windows Server 2019
- Windows Server 2019 (Server Core installation)
- Windows Server 2022
- Windows Server 2022 (Server Core installation)
- Windows Server 2022, 23H2 Edition (Server Core installation)
- Windows Server 2025
- Windows Server 2025 (Server Core installation)