EUVD-2026-43790
GHSA-2jv5-2qvr-82qr
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Network-reachable LSASS with no auth or interaction and low complexity (AV:N/AC:L/PR:N/UI:N); impact is availability-only service crash, so C:N/I:N/A:H, scope unchanged.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
2DescriptionCVE.org
Memory allocation with excessive size value in Windows Local Security Authority Subsystem Service (LSASS) allows an unauthorized attacker to deny service over a network.
AnalysisAI
Denial of service in the Windows Local Security Authority Subsystem Service (LSASS) allows a remote, unauthenticated attacker to crash the service and disrupt authentication across all supported Windows client and server releases from Windows 10 1607 through Windows 11 26H1 and Windows Server 2012 through Server 2025. The flaw stems from an excessive-size memory allocation (CWE-789) triggerable over the network with no privileges or user interaction, and while a vendor patch is available, there is no public exploit identified at time of analysis and it is not listed in CISA KEV. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | No special conditions - remote unauthenticated exploitation against default configurations of Windows LSASS (AV:N/AC:L/PR:N/UI:N). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, base 7.5 HIGH) indicates a remotely reachable, low-complexity, unauthenticated availability-only attack - a realistic and easily repeatable DoS. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with network reachability to an unpatched Windows host sends a crafted authentication-related request containing a malicious oversized length field, causing LSASS to attempt an excessive memory allocation and crash. Because LSASS underpins logon and token issuance, the crash disrupts authentication and can destabilize or reboot the host; the attack requires no credentials or user interaction and, being automatable, can be scripted against many hosts. … |
| Remediation | Apply the Microsoft security update for CVE-2026-40378 as the primary fix - Patch available per vendor advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40378; consult the MSRC update guide for the exact fixed build number matching each affected SKU, as specific patched version numbers were not provided in this data set and should not be invented. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Immediately inventory all Windows 10, Windows 11, and Windows Server (2012-2025) systems in your environment. …
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External POC / Exploit Code
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