Windows Local Security Authority Subsystem Service (LSASS)
CVE-2026-40378 — Windows Local Security Authority Subsystem Service (LSASS) Denial of Service Vulnerability
Executive Summary
Memory allocation with excessive size value in Windows Local Security Authority Subsystem Service (LSASS) allows an unauthorized attacker to deny service over a network.
Overview
7.5
CVSS HIGH
Important
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
CVSS Vector
ATTACK VECTOR
Network
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
None
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
None
INTEGRITY
None
AVAILABILITY
High
EXPLOIT CODE MATURITY
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 6.5
EPSS Score
No EPSS score available for this CVE.
View on FIRST.orgAffected Products
29 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Windows 10 Version 1607 for 32-bit Systems | 5099535 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1607 for x64-based Systems | 5099535 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1809 for 32-bit Systems | 5099538 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1809 for x64-based Systems | 5099538 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 21H2 for 32-bit Systems | 5099539 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 21H2 for ARM64-based Systems | 5099539 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 21H2 for x64-based Systems | 5099539 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 22H2 for 32-bit Systems | 5099539 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 22H2 for ARM64-based Systems | 5099539 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 22H2 for x64-based Systems | 5099539 (Security Update) |
Important | Denial of Service | Yes |
| Windows 11 Version 23H2 for ARM64-based Systems | 5099414 (Security Update) |
Important | Denial of Service | Yes |
| Windows 11 Version 23H2 for x64-based Systems | 5099414 (Security Update) |
Important | Denial of Service | Yes |
| Windows 11 Version 24H2 for ARM64-based Systems | 5101650 (Security Update) |
Important | Denial of Service | Yes |
| Windows 11 Version 24H2 for x64-based Systems | 5101650 (Security Update) |
Important | Denial of Service | Yes |
| Windows 11 Version 25H2 for ARM64-based Systems | 5101650 (Security Update) |
Important | Denial of Service | Yes |
| Windows 11 Version 25H2 for x64-based Systems | 5101650 (Security Update) |
Important | Denial of Service | Yes |
| Windows 11 Version 26H1 for ARM64-based Systems | 5095051 (Security Update) |
Important | Denial of Service | Yes |
| Windows 11 version 26H1 for x64-based Systems | 5095051 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server 2012 | 5099445 (Monthly Rollup) |
Important | Denial of Service | Yes |
| Windows Server 2012 (Server Core installation) | 5099445 (Monthly Rollup) |
Important | Denial of Service | Yes |
| Windows Server 2012 R2 | 5099444 (Monthly Rollup) |
Important | Denial of Service | Yes |
| Windows Server 2012 R2 (Server Core installation) | 5099444 (Monthly Rollup) |
Important | Denial of Service | Yes |
| Windows Server 2016 | 5099535 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server 2016 (Server Core installation) | 5099535 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server 2019 | 5099538 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server 2019 (Server Core installation) | 5099538 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server 2022 | 5099540 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server 2025 | 5099536 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server 2025 (Server Core installation) | 5099536 (Security Update) |
Important | Denial of Service | Yes |
Patches
10 patches
| Article | Type | Restart |
|---|---|---|
5099535 |
Security Update | Yes |
5099538 |
Security Update | Yes |
5099539 |
Security Update | Yes |
5099414 |
Security Update | Yes |
5101650 |
Security Update | Yes |
5095051 |
Security Update | Yes |
5099445 |
Monthly Rollup | Yes |
5099444 |
Monthly Rollup | Yes |
5099540 |
Security Update | Yes |
5099536 |
Security Update | Yes |
Known Exploits
No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.
Acknowledgments
WARP & MORSE teams at Microsoft
References
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