CVE-2026-40397

HIGHNVD 7.87.8—

7.8

Integer underflow (wrap or wraparound) in Windows Common Log File System Driver allows an authorized attacker to elevate privileges locally.

CVSS v3: 7.8
EG Score: 7.8(high)
EPSS: 20.8%
KEV: Not listed

Published

May 12, 2026

Last Modified

May 15, 2026

Advisory Details (1)

Auto-updated May 12, 2026

Patch available. Sources: microsoft.

microsoft Patch Available

Security Update Guide - Microsoft Security Response Center

Security Update Guide - Microsoft Security Response Center. Patch available via Microsoft Security Update

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40397

Vendor Advisories for CVE-2026-40397(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

CVE-2026-40397
Microsoft Security Response Center (MSRC)Elevation of Privilege
Windows Common Log File System Driver Elevation of Privilege Vulnerability

Frequently asked(5)

What is CVE-2026-40397?

CVE-2026-40397 is a high vulnerability published on May 12, 2026. Integer underflow (wrap or wraparound) in Windows Common Log File System Driver allows an authorized attacker to elevate privileges locally.

When was CVE-2026-40397 disclosed?

CVE-2026-40397 was first published in the National Vulnerability Database on May 12, 2026, with the most recent update on May 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2026-40397 actively exploited?

CVE-2026-40397 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 20.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2026-40397?

CVE-2026-40397 has a CVSS v3 base score of 7.8 (NVD).

How do I remediate CVE-2026-40397?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-40397, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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CVE-2026-40397

📅 Published

🔄 Last Modified

📋 Advisory Details (1)