Windows NTLM: Exposure of sensitive information enables spoofing
Summary
Windows clients and servers that use NTLM authentication are affected by CVE-2026-121680. An unauthorized attacker on the network can exploit the exposure of sensitive information in NTLM to perform spoofing, which mainly leads to exposure of credentials. No privileges are required, and the CVSS vector assumes no user interaction, which is the vendor's assessment and not independently verified.
Affected
- Windows 10 Version 1607 and Windows Server 2016 (including Server Core): builds before 10.0.14393.9688
- Windows 10 Version 1809 and Windows Server 2019 (including 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 2022: builds before 10.0.20348.5870
Fixed in
- Cumulative update that brings each product to the listed build number or later
- KB numbers: Unknown, see the MSRC advisory
Workaround
Unknown.
Exploitation
- No exploitation in the wild and no public proof of concept found in the sources reviewed
- CVSS temporal metric E:U (Unproven exploit maturity)
- Whether MSRC flags exploitation: Unknown
Our recommendation
- Patch clients and servers that are still in support to the listed builds or later, starting with domain controllers and file servers
- Check whether any system runs an outdated build or an unsupported Windows version, and plan separately for those
- Block outbound SMB (TCP 445) and HTTP/WebDAV authentication to the internet at the firewall
- Restrict NTLM where possible and enable NTLM auditing to monitor its use
- Re-check the MSRC advisory for KB numbers, mitigations and exploitation status
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Spoofing – Windows NTLM
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates), Microsoft Office
- 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-2026-121680 msrc.microsoft.com
- CVE.org record CVE-2026-121680 www.cve.org
- strix.ai: CVE-2026-121680 (secondary mirror) www.strix.ai
- Dark Reading: NTLM flaw exploited by multiple groups (context on CVE-2025-24054) www.darkreading.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, 05:21.
Original description (NVD)
Exposure of sensitive information to an unauthorized actor in Windows NTLM allows an unauthorized attacker to perform spoofing 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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