# CVE-2026-20872: Microsoft Windows NTLM spoofing via external file path control

Source: https://junglewise.ai/threats/cve-2026-20872-microsoft-windows-ntlm-spoofing-via-external-file-path-control  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-01-13. Updated: 2026-07-30  
License: CC BY 4.0 with a link back

CVE-2026-20872 · Severity: medium · CVSS 6.5 · Published 2026-01-13

A spoofing vulnerability exists in the Windows NTLM authentication protocol, which is used to verify user identities across corporate networks. An attacker could exploit this to trick a system into interacting with a malicious file path, potentially leading to the unauthorized disclosure of sensitive information. This could allow an attacker to impersonate legitimate users or services, compromising the integrity of network communications.

Technologies: [Microsoft Windows 11](https://junglewise.ai/threats/technologies/windows-11), [Microsoft Windows Server 2008 R2](https://junglewise.ai/threats/technologies/windows-server-2008-r2), [Microsoft Windows 10](https://junglewise.ai/threats/technologies/windows-10). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-20872 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20872 being exploited in the wild.

**How severe is CVE-2026-20872?** Medium severity, with a CVSS score of 6.5, published 13 January 2026.

**Which products and versions are affected?** Microsoft Windows 11 22H2, 23H2, 24H2, 25H2; Microsoft Windows Server 2008 R2 Service Pack 1; Microsoft Windows 10 1607, 1809, 21H2, 22H2.

**Is there a fix for CVE-2026-20872?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-20872 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-20872?** Check whether you run Microsoft Windows 11, Microsoft Windows Server 2008 R2 or Microsoft Windows 10 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A spoofing vulnerability exists in Windows NTLM due to improper validation of user-supplied input affecting file names or paths (CWE-73). An unauthenticated attacker can exploit this over the network by inducing a user to perform a specific action, such as clicking a link or visiting a malicious site (User Interaction required). Successful exploitation allows the attacker to control file paths used by the NTLM protocol, which can be leveraged for spoofing attacks or sensitive information disclosure. Microsoft has released security updates to address this vulnerability across multiple versions of Windows and Windows Server.

## Affected products

- Microsoft Windows 10 1607, 1809, 21H2, 22H2
- Microsoft Windows 11 22H2, 23H2, 24H2, 25H2
- Microsoft Windows Server 2008 R2 Service Pack 1

## Timeline

- 2026-01-13: disclosed
- 2026-01-13: advisory: Microsoft released vendor advisory

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20872](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20872)
- [https://www.vicarius.io/vsociety/posts/cve-2026-20872-detection-script-spoofing-vulnerability-in-windows-ntlm](https://www.vicarius.io/vsociety/posts/cve-2026-20872-detection-script-spoofing-vulnerability-in-windows-ntlm)
- [https://www.vicarius.io/vsociety/posts/cve-2026-20872-mitigation-script-spoofing-vulnerability-in-windows-ntlm](https://www.vicarius.io/vsociety/posts/cve-2026-20872-mitigation-script-spoofing-vulnerability-in-windows-ntlm)

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