Microsoft Windows Message Queuing: Remote code execution via double free

Summary

A double free vulnerability in Windows Message Queuing (MSMQ) allows an unauthorized attacker to execute code remotely over the network. The CVSS vector rates the attack complexity as high and requires no user interaction. Systems without MSMQ installed are not affected, and the MSMQ feature is not enabled by default. Conflicting information exists on whether a low-privileged account is required, so the worse case should be assumed until Microsoft confirms it.

Affected

• Windows 10 Version 1607: before 10.0.14393.9688
• Windows 10 Version 1809: before 10.0.17763.9487
• Windows 10 Version 21H2: before 10.0.19044.7846
• Windows 10 Version 22H2: Unknown (version range not confirmed)
• Windows 11 Version 23H2: before 10.0.22631.7711
• Windows 11 Version 24H2: before 10.0.26100.9974
• Windows 11 Version 25H2: before 10.0.26200.9974
• Windows 11 Version 26H1: before 10.0.28000.3501
• Windows 11 Version 26H2: before 10.0.26300.9974
• Windows Server 2016 (including Server Core): before 10.0.14393.9688
• Windows Server 2019 (including Server Core): before 10.0.17763.9487
• Windows Server 2022: before 10.0.20348.5870

Fixed in

• Fixed in the Microsoft November 2026 cumulative updates.
• Exact KB number per operating system: confirm in the MSRC advisory.

Workaround

• Microsoft has not published an official workaround that could be verified.
• If MSMQ is not needed, remove the feature or disable the MSMQ service.
• If MSMQ is needed, restrict access to its ports (TCP 1801 by default) to known application servers only.
• Test changes first, as dependent .NET or line-of-business applications may fail.

Exploitation

• No exploitation in the wild reported.
• No public proof of concept found; status is unknown rather than confirmed absent.
• CISA SSVC: Exploitation none, Automatable no, Technical Impact total.

Our recommendation

• Check whether MSMQ is installed and reachable (Get-WindowsOptionalFeature -Online -FeatureName MSMQ-Container and Get-Service MSMQ).
• Install the November 2026 security update on affected systems, prioritising servers and systems reachable from untrusted networks, in the next maintenance window.
• If patching is delayed, apply the workarounds above.
• Monitor for exploitation reports and for confirmation from Microsoft of the privilege requirement.

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

• MSRC Security Update Guide msrc.microsoft.com
• CVE.org CVE Record www.cve.org
• ZDI November 2026 security update review www.thezdi.com
• Microsoft Learn: MS-MQRR overview learn.microsoft.com
• Senserva KB 5132059 senserva.com
• Strix AI CVE-2026-119964 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, 01:36.