SOURCE FACT
Microsoft · Windows
Microsoft Windows Ancillary Function Driver for WinSock contains a heap-based buffer overflow vulnerability that allows for privilege escalation, enabling a local attacker to gain SYSTEM privileges.
Required action
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
CISA notes
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21418 ; https://nvd.nist.gov/vuln/detail/CVE-2025-21418
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