CVE Watch—

CVE-2025-21418

Microsoft Windows Ancillary Function Driver for WinSock Heap-Based Buffer Overflow Vulnerability

CVSS

—

No CVSS

EPSS

1.6%

p75

KEV

YES

Feb 11, 2025

Exploit Today

0-100

Published: — · Last modified: —

EPSS · 30d

1.6%EPSS · 30 days1.6%

2026-09-172026-10-15

KEV catalog record

Product

Microsoft / Windows

Vulnerability

Microsoft Windows Ancillary Function Driver for WinSock Heap-Based Buffer Overflow Vulnerability

Added to KEV

Feb 11, 2025

Remediate by

Mar 4, 2025

Known ransomware use

Summary description

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.

Notes

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21418 ; https://nvd.nist.gov/vuln/detail/CVE-2025-21418

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