Windows Client for NFS: Local privilege escalation due to race condition

Summary

A race condition in the Windows Client for NFS feature allows a local attacker with low privileges to elevate their privileges, potentially to full control of the host. No user interaction is required and the attack complexity is low. Only systems with the optional NFS client feature enabled are affected, and the flaw cannot be exploited remotely.

Affected

• Windows 10 Version 1607: 10.0.14393.0 to before 10.0.14393.9688
• Windows 10 Version 1809: 10.0.17763.0 to before 10.0.17763.9487
• Windows 10 Version 21H2: 10.0.19044.0 to before 10.0.19044.7846
• Windows 10 Version 22H2: 10.0.19045.0 to before 10.0.19045.7846
• Windows 11 Version 23H2: 10.0.22631.0 to before 10.0.22631.7711
• Windows 11 Version 24H2: 10.0.26100.0 to before 10.0.26100.9974
• Windows 11 Version 25H2: 10.0.26200.0 to before 10.0.26200.9974
• Windows 11 Version 26H1: 10.0.28000.0 to before 10.0.28000.3501
• Windows 11 Version 26H2: 10.0.26300.0 to before 10.0.26300.9974
• Windows Server 2016 (including Server Core): 10.0.14393.0 to before 10.0.14393.9688
• Windows Server 2019 (including Server Core): 10.0.17763.0 to before 10.0.17763.9487
• Windows Server 2022: 10.0.20348.0 to before 10.0.20348.5870
• Note: the version list is taken from the CVE record; verify against the MSRC advisory.

Fixed in

• Install the Microsoft security update for November 2026 (or later) that contains the fixed builds listed above.
• Corresponding KB article numbers: Unknown.

Workaround

• No vendor workaround known.
• If patching is delayed, uninstall or disable the Client for NFS feature on endpoints that do not need to mount NFS shares. This is a general recommendation and not confirmed for this CVE.

Exploitation

• CISA SSVC: exploitation none, not automatable, total technical impact.
• No public proof-of-concept or exploitation reports found at the time of writing.
• Exploit maturity in the CVE vector is unproven (E:U).

Our recommendation

• Identify hosts with Windows Client for NFS enabled, including NFS client mounts on file servers.
• Prioritise patching for Windows 10 1607, 1809 and 21H2 endpoints still in use and for all hosts where NFS is actively used.
• Include the other affected systems in the regular monthly patch cycle.
• Verify installed build numbers and the KB article on the MSRC advisory after patching.
• Restrict local logon and monitor for unusual privilege changes on affected hosts.

Public exploits iAttack code is publicly available (PoC on GitHub, Metasploit or Exploit-DB).

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

• Microsoft Security Update Guide: CVE-2026-118138 msrc.microsoft.com
• CVE Record CVE-2026-118138 (CVE.org) www.cve.org
• Strix.ai CVE-2026-118138 (secondary, unverified versions) 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, 04:02.