Local privilege escalation via use-after-free
Published Feb 10, 2026 · Updated Feb 10, 2026
Use-after-free in Microsoft Windows Cluster Client Failover allows local authenticated users to elevate privileges on affected servers. Public records identify stale-object access in the CCF component but do not disclose the specific allocation, release, or dereference path. The attacker must already have low-privilege local access; no separate user interaction is required, and successful exploitation elevates privileges within the server.
Summary
What happened
Use-after-free in Microsoft Windows Cluster Client Failover allows local authenticated users to elevate privileges on affected servers. Public records identify stale-object access in the CCF component but do not disclose the specific allocation, release, or dereference path. The attacker must already have low-privilege local access; no separate user interaction is required, and successful exploitation elevates privileges within the server.
The record
- CVE
- CVE-2026-21251
- Published
- Feb 10, 2026
- Updated
- Feb 10, 2026
- Vendor
- Microsoft
- Product
- Windows Server 2019
- 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=10.0.17763.0 <10.0.17763.8389
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
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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