CVE-2026-40397
HighUpdated
Published: 12 May 2026
Published
12 May 2026
Modified
01 June 2026
KEV Added
—
Patch
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CVSS Score v3.1
7.8
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS Score
0.0007
21.0th percentile
Risk Priority
16
60% EPSS · 20% KEV · 20% CVSS
Summary
CVE-2026-40397 is a high-severity Wrap or Wraparound (CWE-191) vulnerability in Microsoft Windows 10 21H2. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 21.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-29659
Vulnerability details
Heap-based buffer overflow in Windows Common Log File System Driver allows an authorized attacker to elevate privileges locally.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
Why these techniques?
Local integer underflow in CLFS driver directly enables kernel-level privilege escalation (T1068).
Confidence: HIGH · MITRE ATT&CK Enterprise v18.1
CVEs Like This One
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CVE-2026-34338Same product: Microsoft Windows 10 1607
CVE-2026-32077Same product: Microsoft Windows 10 1607
CVE-2026-27916Same product: Microsoft Windows 10 1607
CVE-2026-25187Same product: Microsoft Windows 10 1607
CVE-2026-25165Same product: Microsoft Windows 10 1607
Affected Assets
microsoft
windows 10 1607
≤ 10.0.14393.9140 · ≤ 10.0.14393.9140
microsoft
windows 10 1809
≤ 10.0.17763.8755 · ≤ 10.0.17763.8755
microsoft
windows 10 21h2
≤ 10.0.19044.7291 · ≤ 10.0.19044.7291 · ≤ 10.0.19044.7291
microsoft
windows 10 22h2
≤ 10.0.19045.7291 · ≤ 10.0.19045.7291 · ≤ 10.0.19045.7291
microsoft
windows 11 23h2
≤ 10.0.22631.7079 · ≤ 10.0.22631.7079
microsoft
windows 11 24h2
≤ 10.0.26100.8390 · ≤ 10.0.26100.8390
microsoft
windows 11 25h2
≤ 10.0.26200.8390 · ≤ 10.0.26200.8390
microsoft
windows 11 26h1
≤ 10.0.28000.2113 · ≤ 10.0.28000.2113
microsoft
windows server 2012
all versions, r2
microsoft
windows server 2016
≤ 10.0.14393.9140
+4 more product configuration(s) — see NVD for full list
Mitigating Controls
No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.