CVE-2026-20831
Unknown Unknown - Not Provided
TOCTOU Race Condition in Windows WinSock Driver Elevates Privileges

Publication date: 2026-01-13

Last updated on: 2026-01-13

Assigner: Microsoft Corporation

Description
Time-of-check time-of-use (toctou) race condition in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
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Meta Information
Published
2026-01-13
Last Modified
2026-01-13
Generated
2026-06-16
AI Q&A
2026-01-14
EPSS Evaluated
2026-06-14
NVD
CVE-2026-20831
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
microsoft windows_ancillary_function_driver_for_winsock *
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-367 The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
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Executive Summary

This vulnerability is a time-of-check time-of-use (toctou) race condition in the Windows Ancillary Function Driver for WinSock. It allows an authorized attacker to elevate their privileges locally by exploiting the timing issue between checking a condition and using the resource. [1]

Impact Analysis

The vulnerability can allow an authorized attacker to elevate their privileges on the affected Windows system locally. This means the attacker could gain higher-level access than intended, potentially leading to unauthorized actions or control over the system. [1]

Mitigation Strategies

Apply the security updates provided by Microsoft for this vulnerability as soon as possible to mitigate the elevation of privilege risk caused by the toctou race condition in the Windows Ancillary Function Driver for WinSock. [1]

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