Windows Message Queuing: Use-after-free allows local privilege escalation

Summary

A use-after-free flaw in the Windows Message Queuing (MSMQ) Queue Manager allows an authorized local attacker with low privileges to elevate privileges. The issue affects systems where the MSMQ Queue Manager service is enabled. Vendor data indicates local attack only (AV:L), and Microsoft rates it Important with CVSS 7.8.

Affected

• Windows 10 Version 1607 (10.0.14393.0 to < 10.0.14393.9612)
• Windows 10 Version 1809 (10.0.17763.0 to < 10.0.17763.9376)
• Windows 10 Version 21H2 (10.0.19044.0 to < 10.0.19044.7807)
• Windows 10 Version 22H2 (10.0.19045.0 to < 10.0.19045.7807)
• Windows 11 Version 23H2 (10.0.22631.0 to < 10.0.22631.7652)
• Windows 11 Version 24H2 (10.0.26100.0 to < 10.0.26100.9711)
• Windows 11 Version 25H2 (10.0.26200.0 to < 10.0.26200.9711)
• Windows 11 Version 26H1 (10.0.28000.0 to < 10.0.28000.3231)
• Windows 11 Version 26H2 (10.0.26300.0 to < 10.0.26300.9711)
• Windows Server 2012 and Server Core (6.2.9200.0 to < 6.2.9200.26434)
• Windows Server 2012 R2 and Server Core (6.3.9600.0 to < 6.3.9600.23470)
• Windows Server 2016 (10.0.14393.0 to < 10.0.14393.9612)

Fixed in

• Install the October 2026 security update for your edition.
• Windows 10 1607 / Server 2016: 10.0.14393.9612 or newer (Microsoft's release information lists a later build, 14393.9615, from an out-of-band update; use the newest).
• Windows 10 1809: 10.0.17763.9376 or newer.
• Windows 10 21H2: 10.0.19044.7807 or newer.
• Windows 10 22H2: 10.0.19045.7807 or newer.
• Windows 11 23H2: 10.0.22631.7652 or newer.
• Windows 11 24H2: 10.0.26100.9711 or newer.
• Windows 11 25H2: 10.0.26200.9711 or newer.
• Windows 11 26H1: 10.0.28000.3231 or newer.
• Windows 11 26H2: 10.0.26300.9711 or newer.
• Windows Server 2012 / Server Core: 6.2.9200.26434 or newer.
• Windows Server 2012 R2 / Server Core: 6.3.9600.23470 or newer.
• KB numbers for Windows 10 1607 were not confirmed.

Workaround

• None needed if the Microsoft update is installed.
• If MSMQ is not required on a host, disabling the feature removes the exposed component. Test first, because dependent applications may break.

Exploitation

• No evidence of exploitation in the wild.
• No public proof-of-concept found.
• CISA SSVC: exploitation none, automatable no, technical impact total.
• EPSS 0.00245 (very low).

Our recommendation

• Check whether MSMQ is installed and enabled on all Windows hosts, including servers and terminal servers.
• Install the October 2026 cumulative updates, using the newest build for each edition.
• Plan the replacement or isolation of Windows 10 1607 LTSB devices, which are out of support after 13 October 2026.
• Restrict local logon on shared servers and monitor for privilege escalation activity.

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-2026-85860 msrc.microsoft.com
• SentinelOne Vulnerability Database: CVE-2026-85860 www.sentinelone.com
• VulDB: CVE-2026-85860 vuldb.com
• Vulners VulnRichment: CVE-2026-85860 vulners.com
• Microsoft Windows release information learn.microsoft.com
• Windows 10 LTSB end of support (Insentra) www.insentragroup.com
• Windows Server 2016 (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, 01:55.