Windows LSASS: Denial of service through heap-based buffer overflow
Summary
Microsoft has fixed a heap-based buffer overflow in the Windows Local Security Authority Subsystem Service (LSASS), component lsasrv, in its November 2026 security updates. An attacker with a valid low-privilege account and a network path to the system can crash the service, causing a denial of service. Confidentiality and integrity are not affected. Microsoft rates the issue Important (CVSS 6.5).
Affected
- Windows 10 Version 1607, 1809, 21H2 and 22H2
- Windows 11 Version 23H2, 24H2, 25H2, 26H1 and 26H2
- Windows Server 2016, 2019 and 2022 (including Server Core installations)
- Exact affected build ranges: see the CVE record. Sources conflict on some builds (for example Windows 11 24H2 / Server 2025: 10.0.26100.33822 or 10.0.26100.9974).
Fixed in
- Fixed in the November 2026 Microsoft security update.
- Build numbers per product are not fully confirmed. The CVE record lists 10.0.14393.9688 (1607), 10.0.17763.9487 (1809), 10.0.22631.7711 (23H2) and others.
- Check the MSRC Security Update Guide for the exact fixed build and KB number for each system.
Workaround
Unknown. No workaround from Microsoft was found in the sources reviewed.
Exploitation
- No public exploit and no known in-the-wild exploitation at the time of research.
- CISA SSVC: exploitation none, not automatable, partial technical impact.
- Third-party sources differ on exploit availability; monitor for changes.
Our recommendation
- Install the November 2026 Microsoft security update on all affected Windows and Server systems, starting with domain controllers and shared or internet-facing servers.
- Identify legacy systems (Windows 10 1607/1809, Server 2016/2019) and patch them with priority.
- Limit network access to LSASS-hosting systems and enforce strong account controls to reduce the risk of misuse of low-privilege accounts.
- Monitor the MSRC page for updates on exploitation status.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Denial of service – Microsoft Local Security Authority Server (lsasrv)
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5131085, KB5131090, KB5131096, KB5131080, KB5131077, KB5132061
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-112807 msrc.microsoft.com
- CVE Record CVE-2026-112807 www.cve.org
- VulDB entry 434882 vuldb.com
- Strix: CVE-2026-112807 www.strix.ai
- Cybersecurity News: Microsoft November 2026 Patch Tuesday cybersecuritynews.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 12:27.
Original description (NVD)
Heap-based buffer overflow in Microsoft Local Security Authority Server (lsasrv) allows an authorized attacker to deny service over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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