Microsoft Windows Kerberos: Denial of service through memory leak
Summary
A missing memory release in the Kerberos implementation of Windows allows an unauthenticated attacker on the network to cause a denial of service. Successful exploitation affects availability only, with no confidentiality or integrity impact. Windows 10, Windows 11 and Windows Server 2016 to 2022 are affected, and domain controllers and other Kerberos-facing servers are the most relevant systems.
Affected
- Windows 10 Version 1607 (Server 2016 also, incl. Server Core): builds before 10.0.14393.9688
- Windows 10 Version 1809 (Server 2019 also, incl. Server Core): builds before 10.0.17763.9487
- Windows 10 Version 21H2: builds before 10.0.19044.7846
- Windows 10 Version 22H2: builds before 10.0.19045.7846
- Windows 11 Version 23H2: builds before 10.0.22631.7711
- Windows 11 Version 24H2: builds before 10.0.26100.9974
- Windows 11 Version 25H2: builds before 10.0.26200.9974
- Windows 11 Version 26H1: builds before 10.0.28000.3501
- Windows 11 Version 26H2: builds before 10.0.26300.9974
- Windows Server 2019 (incl. Server Core): builds before 10.0.17763.9487
- Windows Server 2022: builds before 10.0.20348.5870
- Windows Server 2016 (incl. Server Core): builds before 10.0.14393.9688
Fixed in
- Fixed in the November 2026 security update for each branch, at the builds listed above or later
- Verify the exact KB per system in the MSRC Security Update Guide product table, as the KB numbers from secondary sources are not confirmed.
Workaround
Unknown.
Exploitation
- Microsoft lists the vulnerability as not exploited.
- CISA SSVC: exploitation none, automatable yes, technical impact partial.
- No public proof of concept was found, and no CISA KEV listing was found at the time of research.
Our recommendation
- Apply the November 2026 Windows security update on domain controllers and other Kerberos-facing servers first, after verifying the correct KB on MSRC.
- Inventory Windows 10 1607/1809 and other affected builds, and plan upgrades where these versions are no longer supported.
- Monitor domain controller memory use, restarts and service stability for several days after patching.
- Check CISA KEV and the MSRC advisory again for changes.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Denial of service – Windows Kerberos
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5131291, KB5131085, KB5131096, KB5131090, KB5131087, KB5132061
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC Security Update Guide: CVE-2026-70240 msrc.microsoft.com
- CVE.org CVE Record: CVE-2026-70240 www.cve.org
- Strix CVE summary (secondary) 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 11 Nov 2026, 05:12.
Original description (NVD)
Missing release of memory after effective lifetime in Windows Kerberos 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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