CVE-2025-21418
Microsoft Windows Ancillary Function Driver for WinSock Heap-Based Buffer Overflow Vulnerability
Microsoft Windows
Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 11 February 2025. US federal agencies were required to remediate it by 4 March 2025.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 2.1%, which is higher than 82.1% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Frequently asked questions
Is CVE-2025-21418 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2025-21418.
What does CVE-2025-21418 affect?
CVE-2025-21418 affects Microsoft Windows. Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
How severe is CVE-2025-21418?
CVE-2025-21418 is rated HIGH with a CVSS base score of 7.8. EPSS puts the probability of exploitation in the next 30 days at 2.1%, higher than 82.1% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 4 March 2025.
How should organisations respond to CVE-2025-21418?
Apply the vendor patch for Microsoft Windows as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.