CVE-2025-21418
Published: February 11, 2025
Official 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.
CISA KEV Advisory
Microsoft Windows Ancillary Function Driver for WinSock Heap-Based Buffer Overflow Vulnerability
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.
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Risk Analysis
This heap-based buffer overflow vulnerability in Microsoft Windows Ancillary Function Driver for WinSock allows for privilege escalation, enabling a local attacker to gain SYSTEM privileges. Its inclusion in CISA's KEV catalog and active exploitation in the wild make it a critical concern, despite the lack of specific CVSS scores. The high EPSS score further emphasizes the urgency.
This vulnerability is actively being exploited in the wild and is listed in CISA's Known Exploited Vulnerabilities catalog. It allows a local attacker to gain SYSTEM privileges through a heap-based buffer overflow.
Apply all available security updates and patches for Microsoft Windows to address this privilege escalation vulnerability. Ensure systems are kept up-to-date and implement robust memory protection mechanisms.
Technical Analysis
CVE-2025-21418 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CISA has added CVE-2025-21418 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
Affected Vendors & Products
Exploit & PoC Resources
All References (2)
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2025-21418 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1