Microsoft Windows: Local privilege escalation in Defender Firewall Service

Summary

A double free weakness (CWE-415) in the Windows Defender Firewall Service allows an authorized local attacker to elevate privileges. The attacker needs a local foothold with low privileges, such as a standard user account, and cannot exploit this remotely. Successful exploitation could give the attacker full control over the affected system.

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

Fixed in

• Install the November 2026 security update for the relevant Windows build (fixed builds as per the vendor record: 10.0.14393.9688, 10.0.17763.9487, 10.0.19044.7846, 10.0.19045.7846, 10.0.22631.7711, 10.0.26100.9974, 10.0.26200.9974, 10.0.28000.3501, 10.0.26300.9974, 10.0.20348.5870)
• Verify the KB numbers and the complete product table in the MSRC advisory

Workaround

Unknown. No vendor workaround was found in the sources reviewed. Patching is the remedy.

Exploitation

• Not publicly disclosed according to the Microsoft CNA record and VulDB; no public proof of concept known
• Microsoft exploitability assessment: Less Likely
• CISA SSVC assessment: Exploitation none, not automatable, total technical impact
• Rapid7 reports that Microsoft is aware of in-the-wild exploitation for one vulnerability published in this cycle; the source does not name it, so it cannot be confirmed whether this CVE is affected

Our recommendation

• Patch affected systems in the November 2026 cycle, starting with servers and administrator workstations
• Prioritize Windows 10 1607, 1809 and 21H2, which often remain in use in SMEs; check their support and ESU status
• Limit local and interactive or remote logons to affected hosts and reduce unnecessary local accounts
• Keep endpoint protection active and monitor for unexpected privilege changes

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 (CNA Microsoft) www.cve.org
• MSRC Security Update Guide msrc.microsoft.com
• VulDB vuldb.com
• Rapid7 Patch Tuesday November 2026 www.rapid7.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, 04:18.