Microsoft Windows 11: Elevation of privilege in Windows Defender Firewall Service
Summary
A use-after-free flaw (CWE-416) in the Windows Defender Firewall Service allows an authorized local attacker to elevate privileges on the affected system. The attacker needs a low-privileged account on the host, so the flaw is not remotely exploitable by itself. Microsoft rates the CVSS 3.1 base score at 7.8 (High).
Affected
- Windows 11 23H2: builds before 10.0.22631.7652 (conflicting secondary sources list 22621.7652, to be verified)
- Windows 11 24H2: builds before 10.0.26100.9711
- Windows 11 25H2: builds before 10.0.26200.9711
- Windows 11 26H1: builds before 10.0.28000.3231
- Windows 11 26H2: builds before 10.0.26300.9711
- Windows Server 2025 (including Server Core): builds before 10.0.26100.33650
Fixed in
- Windows 11 23H2: 10.0.22631.7652 (KB5126653, to be verified)
- Windows 11 24H2, 25H2, 26H2: KB5127648 (10.0.26100.9711 / 10.0.26200.9711 / 10.0.26300.9711)
- Windows 11 26H1: KB5127646 (10.0.28000.3231)
- Windows Server 2025: 10.0.26100.33650 (KB number unknown)
Workaround
Unknown. No vendor-published workaround was found.
Exploitation
- Microsoft marks the flaw as not publicly disclosed, with exploit code maturity Unproven.
- EPSS score: 0.00361.
- No evidence of in-the-wild exploitation or public proof-of-concept code was found.
- CISA SSVC: exploitation none, automatable no, technical impact total.
Our recommendation
- Install the October 13, 2026 cumulative update on all affected Windows 11 and Windows Server 2025 systems.
- Prioritise shared workstations, RDP or terminal servers and Server 2025 hosts.
- Replace unsupported Windows 11 23H2 Home or Pro devices, as they will not receive this fix.
- Verify the fixed build for 23H2 against the MSRC KB article before relying on it.
- Recheck the CISA KEV catalogue for changes in exploitation status.
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC Security Update Guide: CVE-2026-83679 msrc.microsoft.com
- Vulners CVE-2026-83679 (CNA JSON) vulners.com
- Microsoft message center MC1506288 mc.merill.net
- BleepingComputer: KB5127648 and KB5126653 released www.bleepingcomputer.com
- Strix CVE-2026-83679 www.strix.ai
- Windows 11 version history (Wikipedia) en.wikipedia.org
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 2 Nov 2026, 03:23.
Original description (NVD)
Use after free in Windows Defender Firewall Service allows an authorized attacker to elevate privileges locally.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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