Local privilege escalation via kernel-memory TOCTOU race
Published Jan 13, 2026 · Updated Jan 13, 2026
TOCTOU race condition in Windows Kernel Memory allows local users to elevate privileges through local access on affected systems. Microsoft identifies Windows Kernel Memory and a heap-based buffer overflow, but has not disclosed the checked resource, competing operation, or vulnerable function that creates the race. Successful exploitation requires existing low-privilege access and grants elevated control over the affected Windows host.
Summary
What happened
TOCTOU race condition in Windows Kernel Memory allows local users to elevate privileges through local access on affected systems. Microsoft identifies Windows Kernel Memory and a heap-based buffer overflow, but has not disclosed the checked resource, competing operation, or vulnerable function that creates the race. Successful exploitation requires existing low-privilege access and grants elevated control over the affected Windows host.
The record
- CVE
- CVE-2026-20809
- Published
- Jan 13, 2026
- Updated
- Jan 13, 2026
- Vendor
- Microsoft
- Product
- Windows Server 2019
- Classifications
- CWE-122, CWE-367, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jan 13, 2026CVE publishedPublication date reported by the CVE source.
- Jan 13, 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 <10.0.17763.8276
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.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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