Windows FTP Service: Local privilege escalation due to improper authorization

Summary

Improper authorization in the Windows FTP Service allows a local user with valid, low-privileged credentials to elevate their privileges on the affected host. Successful exploitation could give the attacker high impact on confidentiality, integrity and availability. The vector is local (AV:L) and requires low privileges, so an attacker must first gain a local account, for example through phishing, a stolen password or a malicious insider.

Affected

• Windows 10 Version 1607 and Windows Server 2016 (including Server Core): 10.0.14393.0 before 10.0.14393.9688
• Windows 10 Version 1809 and Windows Server 2019 (including Server Core): 10.0.17763.0 before 10.0.17763.9487
• Windows 10 Version 21H2: 10.0.19044.0 before 10.0.19044.7846
• Windows 10 Version 22H2: 10.0.19045.0 before 10.0.19045.7846
• Windows 11 Version 23H2: 10.0.22631.0 before 10.0.22631.7711
• Windows 11 Version 24H2: 10.0.26100.0 before 10.0.26100.9974
• Windows 11 Version 25H2: 10.0.26200.0 before 10.0.26200.9974
• Windows 11 Version 26H1: 10.0.28000.0 before 10.0.28000.3501
• Windows 11 Version 26H2: 10.0.26300.0 before 10.0.26300.9974
• Windows Server 2022: 10.0.20348.0 before 10.0.20348.5870

Fixed in

Fixed in Microsoft's November 2026 security updates (released 2026-11-10). Specific KB numbers per Windows version: Unknown.

Workaround

Unknown.

Exploitation

• No evidence of exploitation in the wild found at the time of writing.
• No public proof-of-concept found.
• Microsoft's temporal score uses E:U (exploit code maturity 'unproven').
• CISA SSVC: Exploitation none, Automatable no, Technical Impact total.

Our recommendation

• Check whether the Windows FTP Service is installed and running on your servers and workstations (for example with Get-WindowsFeature or the Optional Features view).
• Disable the FTP service on hosts where it is not required.
• Install the November 2026 security updates on affected builds, prioritising hosts where FTP is enabled and used by several users.
• Verify the affected builds and KB numbers against the Microsoft Security Response Center advisory before rollout.
• Monitor for unexpected privilege changes and new local administrator accounts.

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-2026-118137 msrc.microsoft.com
• CVE Record: CVE-2026-118137 www.cve.org
• Tenable: Microsoft November 2026 Patch Tuesday www.tenable.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, 04:01.