Microsoft Windows: Privilege escalation via double free in Multiple Provider Router

Summary

Microsoft Windows contains a double free vulnerability in the Windows Multiple Provider Router, tracked as CVE-2026-118220. A local attacker with low privileges and no user interaction can exploit it to elevate privileges. The attacker needs an existing foothold on the system, for example through a compromised user account or malware, because the flaw is not directly reachable from the network.

Affected

• Windows 10 Version 1607 (10.0.14393.0 before 10.0.14393.9688)
• Windows 10 Version 1809 (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 2016, including Server Core (10.0.14393.0 before 10.0.14393.9688)
• Windows Server 2019, including Server Core (10.0.17763.0 before 10.0.17763.9487)
• Windows Server 2022 (10.0.20348.0 before 10.0.20348.5870)

Fixed in

• Install the Microsoft security update for November 2026. The fixed build is the value listed for your edition; the build number must be equal to or higher.
• KB article numbers for this CVE: Unknown.

Workaround

Unknown. No Microsoft workaround or mitigation is known for this CVE.

Exploitation

• No public proof of concept known.
• No evidence of in-the-wild exploitation found.
• No CISA KEV entry found.
• CISA SSVC: Exploitation none, Automatable no, Technical Impact total.

Our recommendation

• Patch all affected Windows 10, Windows 11 and Windows Server systems with the November 2026 update, with priority on shared workstations, RDP or terminal servers and hosts with untrusted users.
• Check the build number after patching against the fixed value for your edition.
• Identify and replace Windows 10 systems that are no longer supported.
• Monitor for unexpected privilege escalation 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

• CVE Record CVE-2026-118220 (Microsoft CNA) www.cve.org
• Microsoft Security Update Guide CVE-2026-118220 msrc.microsoft.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, 03:57.