Windows LSASS: Denial of service via out-of-bounds read
Summary
An out-of-bounds read in the Windows Local Security Authority Subsystem Service (LSASS) allows an unauthorized attacker to cause a denial of service over the network. Only availability is rated as affected; no confidentiality or integrity impact is listed. No login or user interaction is required, but the sources do not state which network service reaches the vulnerable code path.
Affected
- Windows 10 Version 1809: 10.0.17763.0 to below 10.0.17763.9376
- Windows Server 2019 (incl. Server Core): 10.0.17763.0 to below 10.0.17763.9376
- Windows Server 2022: 10.0.20348.0 to below 10.0.20348.5761
- Windows Server 2025 (incl. Server Core): 10.0.26100.0 to below 10.0.26100.33650
- Windows 11 24H2: 10.0.26100.0 to below 10.0.26100.9711
- Windows 11 25H2: 10.0.26200.0 to below 10.0.26200.9711
- Windows 11 26H1: 10.0.28000.0 to below 10.0.28000.3231
- Windows 11 26H2: 10.0.26300.0 to below 10.0.26300.9711
Fixed in
- Fixed builds as listed in the affected ranges above (Windows 10 1809 / Server 2019: 10.0.17763.9376)
- Knowledge base for Windows 10 1809 / Server 2019 reported as KB5126651 by a third-party aggregator; not confirmed on Microsoft's site
- Confirm all builds on the MSRC advisory before deployment
Workaround
Unknown.
Exploitation
- Not listed in the CISA KEV catalog
- CISA SSVC: exploitation none, automatable no, technical impact partial
- EPSS about 1.4%
- No public proof of concept found in research; this does not prove none exists
- Microsoft's exploitation and public disclosure flags are unknown
Our recommendation
- Install the Microsoft security update for the affected builds, starting with domain controllers and internet-reachable servers
- Check whether Windows 10 1809 and Windows Server 2019 are still in use and still supported, and plan their upgrade
- Verify which servers are reachable from untrusted network segments and restrict access where possible
- Monitor LSASS availability and authentication failures on affected systems
- Priority: moderate by default; raise it for internet-reachable or domain controller systems
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Denial of service – Windows Local Security Authority Subsystem Service (LSASS)
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation unlikely
- Product family
- Windows
- Updates (KB)
- KB5127648, KB5126651, KB5126655, KB5126646, KB5127646
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-83516 msrc.microsoft.com
- OpenCVE: CVE-2026-83516 app.opencve.io
- Vulners (Microsoft): MS:CVE-2026-83516 vulners.com
- Vulners (NVD): CVE-2026-83516 vulners.com
- Strix: CVE-2026-83516 www.strix.ai
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 2 Nov 2026, 18:55.
Original description (NVD)
Out-of-bounds read in Windows Local Security Authority Subsystem Service (LSASS) allows an unauthorized 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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