Local privilege escalation via AFD packet use-after-free
Published Feb 10, 2026 · Updated Feb 10, 2026
Use-after-free in the Windows Ancillary Function Driver for WinSock allows local users to elevate privileges on affected Windows builds. During a race, socket cleanup frees an enqueued I/O mini-completion packet that AfdNotifyRemoveIoCompletion later dequeues and accesses. Exploitation requires low-privileged local access and race timing; successful exploitation grants elevated Windows privileges.
Summary
What happened
Use-after-free in the Windows Ancillary Function Driver for WinSock allows local users to elevate privileges on affected Windows builds. During a race, socket cleanup frees an enqueued I/O mini-completion packet that AfdNotifyRemoveIoCompletion later dequeues and accesses. Exploitation requires low-privileged local access and race timing; successful exploitation grants elevated Windows privileges.
The record
- CVE
- CVE-2026-21241
- Published
- Feb 10, 2026
- Updated
- Feb 10, 2026
- Vendor
- Microsoft
- Product
- Windows Server 2025 (Server Core installation)
- Classifications
- CWE-416, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Feb 10, 2026CVE publishedPublication date reported by the CVE source.
- Feb 10, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.0.26100.0 <10.0.26100.32370
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- Researcher CVE-2026-21241 AFD.sys proof of conceptproof of concept · demonstrated
- Bad-Jubies CVE-2026-21241 crash proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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