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CVE-2025-21418 is an elevation-of-privilege vulnerability in the Windows Ancillary Function Driver for WinSock (AFD.sys), a kernel-mode networking component that brokers Windows Sockets operations between user mode and the kernel. Available reporting identifies the flaw as a heap-based buffer overflow in AFD.sys that can be triggered by a locally authenticated attacker through a specially crafted program. Successful exploitation results in corruption of kernel memory within the driver and enables escalation of privileges from a local user context to NT AUTHORITY\SYSTEM. The vulnerability was reported as actively exploited in the wild at the time of patch release.
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What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
If you can’t patch tonight, do this now.
Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
10 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A previously exploited afd.sys zero-day mentioned as historical context.
A Windows Ancillary Function Driver (AFD) vulnerability (kernel/user boundary) discussed in the context of recent AFD zero-days; treated as a likely elevation-of-privilege issue affecting kernel parsing of user-mode input.
An elevation of privilege vulnerability in the Windows Ancillary Function Driver for WinSock.
A Windows Ancillary Function Driver for WinSock elevation of privilege vulnerability that Microsoft reports is under active exploitation in the wild.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.