CVE-2026-34345 - Vulnerability Details

- Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

Description

Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

Published: 2026-05-12

Score: 7 High

EPSS: n/a

KEV: No

Impact:

Action:

Analysis

Impact

The vulnerability is a race condition in the Windows Ancillary Function Driver for WinSock that allows an authorized user to elevate their privileges on the local system. This flaw is caused by concurrent access to a shared resource without proper synchronization. The CNA identifies the weakness as CWE‑362 (Race Condition) and additionally lists it under CWE‑416 (Use‑After‑Free) without further detail on memory misuse.

Affected Systems

Affected operating systems include Microsoft Windows 10 versions 1607, 1809, 21H2, and 22H2; Windows 11 versions 23H2, 24H2, 25H2, 26H1, and 22H3; and Windows Server versions 2016, 2019, 2022, 2025, and the 23H2 edition. The Server Core installations for Windows Server 2016, 2019, 2022, 2025, and 23H2 are also impacted.

Risk and Exploitability

The CVSS score of 7 indicates a high‑severity local privilege escalation. EPSS is not available, so no quantitative exploitation probability is reported, and the vulnerability is not listed in CISA’s KEV catalog. The attack requires local user access and does not rely on network or remote execution vectors.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Microsoft

Windows 10 Version 1607

affected

Version	Status	Constraints
`10.0.14393.0`	affected	< 10.0.14393.9140

Microsoft

Windows 10 Version 1809

affected

Version	Status	Constraints
`10.0.17763.0`	affected	< 10.0.17763.8755

Microsoft

Windows 10 Version 21H2

affected

Version	Status	Constraints
`10.0.19044.0`	affected	< 10.0.19044.7291

Microsoft

Windows 10 Version 22H2

affected

Version	Status	Constraints
`10.0.19045.0`	affected	< 10.0.19045.7291

Microsoft

Windows 11 version 22H3

affected

Version	Status	Constraints
`10.0.22631.0`	affected	< 10.0.22631.7079

Microsoft

Windows 11 Version 23H2

affected

Version	Status	Constraints
`10.0.22631.0`	affected	< 10.0.22631.7079

Microsoft

Windows 11 Version 24H2

affected

Version	Status	Constraints
`10.0.26100.0`	affected	< 10.0.26100.8457

Microsoft

Windows 11 Version 25H2

affected

Version	Status	Constraints
`10.0.26200.0`	affected	< 10.0.26200.8457

Microsoft

Windows 11 version 26H1

affected

Version	Status	Constraints
`10.0.28000.0`	affected	< 10.0.28000.2113

Microsoft

Windows Server 2016

affected

Version	Status	Constraints
`10.0.14393.0`	affected	< 10.0.14393.9140

Microsoft

Windows Server 2016 (Server Core installation)

affected

Version	Status	Constraints
`10.0.14393.0`	affected	< 10.0.14393.9140

Microsoft

Windows Server 2019

affected

Version	Status	Constraints
`10.0.17763.0`	affected	< 10.0.17763.8755

Microsoft

Windows Server 2019 (Server Core installation)

affected

Version	Status	Constraints
`10.0.17763.0`	affected	< 10.0.17763.8755

Microsoft

Windows Server 2022

affected

Version	Status	Constraints
`10.0.20348.0`	affected	< 10.0.20348.5139

Microsoft

Windows Server 2022, 23H2 Edition (Server Core installation)

affected

Version	Status	Constraints
`10.0.25398.0`	affected	< 10.0.25398.2330

Microsoft

Windows Server 2025

affected

Version	Status	Constraints
`10.0.26100.0`	affected	< 10.0.26100.32860

Microsoft

Windows Server 2025 (Server Core installation)

affected

Version	Status	Constraints
`10.0.26100.0`	affected	< 10.0.26100.32860

No data.

No data available yet.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

Install the Windows security update for CVE‑2026‑34345 from the Microsoft Security Advisory.
Apply the patch to all affected Windows 10, Windows 11, and Windows Server versions listed above.
If the patch cannot be applied immediately, restrict the execution of the WinSock Ancillary Function Driver to administrators and review local user permissions until the fix is deployed.

Generated by OpenCVE AI on May 12, 2026 at 20:51 UTC.

Tracking

Sign in to view the affected projects.

Advisories

No advisories yet.

No CVSS v4.0

Attack Vector Local

Attack Complexity High

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Exploitation none

Automatable no

Technical Impact total

References

Link	Providers
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-34345

History

Tue, 12 May 2026 20:15:00 +0000

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}`

Tue, 12 May 2026 17:30:00 +0000

Type	Values Removed	Values Added
Description		Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
Title		Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
First Time appeared		Microsoft Microsoft windows 10 1607 Microsoft windows 10 1809 Microsoft windows 10 21h2 Microsoft windows 10 22h2 Microsoft windows 11 23h2 Microsoft windows 11 24h2 Microsoft windows 11 25h2 Microsoft windows 11 26h1 Microsoft windows Server 2016 Microsoft windows Server 2019 Microsoft windows Server 2022 Microsoft windows Server 2025 Microsoft windows Server 23h2
Weaknesses		CWE-362 CWE-416
CPEs		cpe:2.3:o:microsoft:windows_10_1607:::::::x86:* cpe:2.3:o:microsoft:windows_10_1809:::::::x86:* cpe:2.3:o:microsoft:windows_10_21H2:::::::x86:* cpe:2.3:o:microsoft:windows_10_22H2:::::::x64:* cpe:2.3:o:microsoft:windows_11_23H2:::::::arm64:* cpe:2.3:o:microsoft:windows_11_23H2:::::::x64:* cpe:2.3:o:microsoft:windows_11_24H2:::::::arm64:* cpe:2.3:o:microsoft:windows_11_25H2:::::::arm64:* cpe:2.3:o:microsoft:windows_11_26H1:::::::x64:* cpe:2.3:o:microsoft:windows_server_2016:::::::: cpe:2.3:o:microsoft:windows_server_2019:::::::: cpe:2.3:o:microsoft:windows_server_2022:::::::: cpe:2.3:o:microsoft:windows_server_2025:::::::: cpe:2.3:o:microsoft:windows_server_23h2::::::::
Vendors & Products		Microsoft Microsoft windows 10 1607 Microsoft windows 10 1809 Microsoft windows 10 21h2 Microsoft windows 10 22h2 Microsoft windows 11 23h2 Microsoft windows 11 24h2 Microsoft windows 11 25h2 Microsoft windows 11 26h1 Microsoft windows Server 2016 Microsoft windows Server 2019 Microsoft windows Server 2022 Microsoft windows Server 2025 Microsoft windows Server 23h2
References		https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-34345
Metrics		cvssV3_1 `{'score': 7, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C'}`

Subscriptions

Microsoft Windows 10 1607 Windows 10 1809 Windows 10 21h2 Windows 10 22h2 Windows 11 23h2 Windows 11 24h2 Windows 11 25h2 Windows 11 26h1 Windows Server 2016 Windows Server 2019 Windows Server 2022 Windows Server 2025 Windows Server 23h2

MITRE

Status: PUBLISHED

Assigner: microsoft

Published: 2026-05-12T16:58:25.988Z

Updated: 2026-05-13T03:57:10.034Z

Reserved: 2026-03-26T21:02:16.446Z

Link: CVE-2026-34345

Vulnrichment

Updated: 2026-05-12T19:45:19.457Z

NVD

Status : Received

Published: 2026-05-12T18:17:09.190

Modified: 2026-05-12T18:17:09.190

Link: CVE-2026-34345

Redhat

No data.

OpenCVE Enrichment

Updated: 2026-05-12T21:00:13Z

Weaknesses

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Local

Attack Complexity High

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

Exploitation none

Automatable no

Technical Impact total

Subscriptions

JSON object

JSON object

JSON object

JSON object

JSON object