Windows Active Directory: Denial of service vulnerability
Summary
A flaw in Windows Active Directory allows an authorized attacker with network access and a valid low-privilege account to cause a denial of service. Per the CVSS vector, only availability is affected, with no confidentiality or integrity impact. Domain controllers are the main concern, because a disruption can affect logons and services across the site.
Affected
- Windows 10 Version 1607 (before 10.0.14393.9688)
- Windows 10 Version 1809 (before 10.0.17763.9487)
- Windows 10 Version 21H2 (before 10.0.19044.7846)
- Windows 10 Version 22H2 (before 10.0.19045.7846)
- Windows 11 Version 23H2 (before 10.0.22631.7711)
- Windows 11 Version 24H2 (before 10.0.26100.9974)
- Windows 11 Version 25H2 (before 10.0.26200.9974)
- Windows 11 Version 26H1 (before 10.0.28000.3501)
- Windows 11 Version 26H2 (before 10.0.26300.9974)
- Windows Server 2016, including Server Core (before 10.0.14393.9688)
- Windows Server 2019, including Server Core (before 10.0.17763.9487)
- Windows Server 2022 (before 10.0.20348.5870)
- Windows Server 2025: affected build range not confirmed by the CVE record; verify on MSRC
Fixed in
- Install the Microsoft security update for your Windows version, which provides the build numbers listed under affected.
- Windows Server 2025: verify the fixed build on the MSRC advisory before rollout.
Workaround
Unknown. No vendor workaround was found. Applying the security update is the remedy.
Exploitation
- Microsoft reports no known exploitation and no public disclosure.
- CISA SSVC: exploitation none, not automatable.
- No public proof of concept is known.
Our recommendation
- Patch domain controllers first in the next update cycle, then other Windows systems.
- Confirm that domain controllers are not directly reachable from the internet.
- Review accounts with network logon rights and remove unused accounts.
- Monitor domain controllers for unexpected Active Directory service crashes or restarts.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Denial of service – Windows Active Directory
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5132061, KB5132043, KB5131085, KB5131090, KB5131096, KB5131080
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-105559 msrc.microsoft.com
- CVE Record CVE-2026-105559 www.cve.org
- VulDB entry 434566 vuldb.com
- Strix CVE summary CVE-2026-105559 www.strix.ai
- Rapid7 Patch Tuesday November 2026 www.rapid7.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, 12:40.
Original description (NVD)
No cwe for this issue in Windows Active Directory 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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