Windows Kerberos: Denial of service via integer overflow
Summary
A flaw in the Windows Kerberos component allows an attacker with a valid low-privilege account to cause a denial of service over the network. The root cause is an integer overflow or wraparound, and the CVE record also lists an out-of-bounds read (CWE-125). A successful attack can crash or hang affected systems, which may disrupt domain authentication. According to the CVSS vector, confidentiality and integrity are not affected.
Affected
- Windows 10 Version 1607 (builds before 10.0.14393.9688)
- Windows 10 Version 1809 (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 2016 including Server Core (builds before 10.0.14393.9688)
- Windows Server 2019 including Server Core (builds before 10.0.17763.9487)
- Windows Server 2022 (builds before 10.0.20348.5870)
Fixed in
- Fixed builds according to the CNA record: see the build numbers above (first fixed build per product).
- KB numbers: Unknown. Verify them in the MSRC advisory before rollout.
- Windows Server 2025: Unknown in the CNA record; a secondary source lists 10.0.26100.33822, which is not confirmed by Microsoft.
Workaround
- Unknown. No workaround was found in the available sources.
- Apply the Microsoft security update.
Exploitation
- No confirmed in-the-wild exploitation reported.
- Rapid7 rates exploitation as unlikely and reports no public disclosure.
- No public proof-of-concept reported; VulDB states that no exploit is available.
Our recommendation
- Confirm your build numbers and KB numbers against the MSRC advisory.
- Patch domain controllers first, then servers and clients, within a maintenance window.
- Block or restrict Kerberos (TCP/UDP 88) from untrusted networks and check for unexpected exposure.
- Monitor for crashes or unexplained authentication failures on domain controllers.
- Re-check NVD and MSRC once NVD analysis is complete.
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 unlikely
- 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-2026-119940 msrc.microsoft.com
- CVE Record CVE-2026-119940 www.cve.org
- VulDB entry 434290 vuldb.com
- Rapid7 Patch Tuesday November 2026 analysis www.rapid7.com
- Senserva KB 5132059 senserva.com
- Strix CVE-2026-119940 (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, 12:07.
Original description (NVD)
Integer overflow or wraparound in Windows Kerberos 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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