Security Digest · Vulnerability record · Known exploited
CVE-2025-21418: Microsoft Windows Ancillary Function Driver for WinSock Heap-Based Buffer Overflow Vulnerability
Exploited in the wild (CISA KEV). Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
CISA KEV · added 2025-02-11 CVSS 7.8 High EPSS 1.6% · p75
Should you act?
Exploited: patch now if you run it
CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Yes, if you run Microsoft Windows. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-02-11, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-03-04; treat that as the outer limit, not the target.
- EPSS 1.6%, percentile 75: FIRST’s model estimates a 1.6% chance of exploitation activity in the next 30 days, higher than 75% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.
What it is
Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
CISA’s summary
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.
Weakness type: CWE-122.
Product: Microsoft Windows · Assigned by: microsoft · Published: 2025-02-11
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| Microsoft | Windows 10 Version 1507 | 10.0.10240.0 < 10.0.10240.20915 |
| Microsoft | Windows 10 Version 1607 | 10.0.14393.0 < 10.0.14393.7785 |
| Microsoft | Windows 10 Version 1809 | 10.0.17763.0 < 10.0.17763.6893 |
| Microsoft | Windows 10 Version 21H2 | 10.0.19044.0 < 10.0.19044.5487 |
| Microsoft | Windows 10 Version 22H2 | 10.0.19045.0 < 10.0.19045.5487 |
| Microsoft | Windows 11 version 22H2 | 10.0.22621.0 < 10.0.22621.4890 |
| Microsoft | Windows 11 version 22H3 | 10.0.22631.0 < 10.0.22631.4890 |
| Microsoft | Windows 11 Version 23H2 | 10.0.22631.0 < 10.0.22631.4890 |
| Microsoft | Windows 11 Version 24H2 | 10.0.26100.0 < 10.0.26100.3194 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 | 6.1.7601.0 < 6.1.7601.27566 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoft | 3.1 | 7.8 High | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C |
- Attack vector: local access needed
- Attack complexity: low
- Privileges required: low (any account)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: added 2025-02-11; federal due date 2025-03-04. Known ransomware use: Unknown.
- CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active, automatable no, technical impact total.
- FIRST EPSS (model of 2026-10-21): 1.57% probability of exploitation activity in the next 30 days; percentile 75.
Timeline
- — Added to CISA’s Known Exploited Vulnerabilities catalog
- — CVE record published by microsoft
- — CISA remediation deadline for US federal agencies
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability msrc.microsoft.com
Vulnerability records
- CVE.org record CVE-2025-21418 cve.org
- NVD entry CVE-2025-21418 nvd.nist.gov
Government
All exploited Microsoft vulnerabilities · Today’s Security Digest