Summary
Impact: Elevation of Privilege. Microsoft rating: Important. Not known to be exploited — Exploitation More Likely. Customer action: Required.
Details
According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability?
For an attacker to exploit this vulnerability, they would need to have knowledge of a specific operation that triggers a memory allocation failure, specifically a use after free.
What privileges could be gained by an attacker who successfully exploited this vulnerability?
An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.
Security updates
10.0.28000.1575 — https://support.microsoft.com/help/5077179
10.0.20348.4773 — https://support.microsoft.com/help/5075906
10.0.20348.4711 — https://support.microsoft.com/help/5075943
10.0.26100.32370 — https://support.microsoft.com/help/5075899
10.0.26100.32313 — https://support.microsoft.com/help/5075942
10.0.26200.7840 — https://support.microsoft.com/help/5077181
10.0.26200.7781 — https://support.microsoft.com/help/5077212
10.0.22631.6649 — https://support.microsoft.com/help/5075941
10.0.25398.2149 — https://support.microsoft.com/help/5075897
Vulnerabilities 1
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High 7.0
Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
Revision history
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#1
Information published.
References
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CVE-2026-21241 Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21241
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss