CVE-2026-40378: Windows Local Security Authority Subsystem Service (LSASS) Denial of Service Vulnerability

highCVSS 7.5CVE-2026-40378

Memory allocation with excessive size value in Windows Local Security Authority Subsystem Service (LSASS) allows an unauthorized attacker to deny service over a network.

CSIRTS triage

vendor: Microsoft product: Windows Local Security Authority Subsystem Service (LSASS)Denial of service

What: Memory allocation with excessive size value in Windows Local Security Authority Subsystem Service (LSASS) allows an unauthorized attacker to deny service over a network.
Who is affected: Deployments of Windows LSASS.
Urgency: Remediation is urgent due to the high severity and potential for denial of service.
Action: Apply the latest security patch for Windows LSASS.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.5
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40378

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-403780.82% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 54% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-40378	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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