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CVE-2026-42911: Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

highCVSS 7CVE-2026-42911
Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

CSIRTS triage

vendor: Microsoftproduct: Windows Ancillary Function Driver for WinSockPrivilege escalation
What
An authorized attacker can elevate privileges locally due to a use-after-free vulnerability.
Who is affected
Users of the Windows Ancillary Function Driver for WinSock are affected.
Urgency
Remediation is high urgency due to the potential for privilege escalation.
Action
Apply the latest security patches.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
high — CVSS 7
Published
2026-06-09
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42911

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-42911coverage & exploitation statusNVD · CVE.org

Recent advisories for Windows Ancillary Function

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

More from Microsoft Security Response Center