CVE-2026-21251: CWE-416: Use After Free in Microsoft Windows Server 2016
Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.
AI Analysis
Technical Summary
This vulnerability (CVE-2026-21251) involves a use-after-free condition in the Windows Cluster Client Failover feature of Windows Server 2016 (version 10.0.14393.0). Exploitation requires local access with some privileges and does not require user interaction. Successful exploitation can lead to elevation of privileges, impacting confidentiality, integrity, and availability. Microsoft has released an official patch to remediate this vulnerability.
Potential Impact
An authorized local attacker can exploit this use-after-free vulnerability to elevate privileges on the affected Windows Server 2016 system. This can lead to full system compromise, affecting confidentiality, integrity, and availability of the system.
Mitigation Recommendations
An official fix is available from Microsoft. Administrators should apply the security update provided in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21251 to remediate this vulnerability.
CVE-2026-21251: CWE-416: Use After Free in Microsoft Windows Server 2016
Description
Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CVE-2026-21251) involves a use-after-free condition in the Windows Cluster Client Failover feature of Windows Server 2016 (version 10.0.14393.0). Exploitation requires local access with some privileges and does not require user interaction. Successful exploitation can lead to elevation of privileges, impacting confidentiality, integrity, and availability. Microsoft has released an official patch to remediate this vulnerability.
Potential Impact
An authorized local attacker can exploit this use-after-free vulnerability to elevate privileges on the affected Windows Server 2016 system. This can lead to full system compromise, affecting confidentiality, integrity, and availability of the system.
Mitigation Recommendations
An official fix is available from Microsoft. Administrators should apply the security update provided in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21251 to remediate this vulnerability.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- microsoft
- Date Reserved
- 2025-12-11T21:02:05.736Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- official-fix
- Vendor Advisory Urls
- [{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21251","vendor":"Microsoft"}]
Threat ID: 698b76004b57a58fa120a031
Added to database: 2/10/2026, 6:16:32 PM
Last enriched: 5/12/2026, 5:12:59 AM
Last updated: 5/22/2026, 2:19:05 AM
Views: 121
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
External Links
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.