EUVD-2026-29584
GHSA-vvg8-qx8v-fp7m
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local authenticated low-priv user (AV:L/PR:L) triggers a low-complexity double free with no interaction, yielding full SYSTEM control, so C/I/A all High.
Primary rating from NVD.
CVSS VectorNVD
Lifecycle Timeline
2DescriptionCVE.org
Double free in Windows Message Queuing allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in Microsoft Windows Message Queuing (MSMQ) allows an authenticated low-privileged user to corrupt kernel/service memory through a double free (CWE-415) and elevate to SYSTEM. It affects a broad range of Windows client and server releases from Windows Server 2012/Windows 10 1607 through Windows 11 26H1 and Windows Server 2025 where the MSMQ feature is installed. There is no public exploit identified at time of analysis, EPSS is very low (0.04%), and CISA SSVC records no known exploitation, though the technical impact is rated total.
Technical ContextAI
Windows Message Queuing (MSMQ) is an optional Windows component (the mqsvc.exe service and associated kernel/driver code, e.g. mqac.sys) that provides asynchronous, store-and-forward messaging between applications. The root cause is a double free (CWE-415): the same heap allocation is released twice, which can corrupt heap metadata or leave a dangling pointer that an attacker grooms and reclaims to gain control of freed memory. In a privileged service context this memory-management error becomes an elevation-of-privilege primitive. The CPE set enumerates Microsoft Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (22H3, 23H2, 24H2, 25H2, 26H1) and Windows Server 2012, confirming the flaw lives in the OS-bundled MSMQ code path rather than a third-party product.
RemediationAI
Apply the Microsoft security update for CVE-2026-33838; this is a Vendor-released patch with fixed builds enumerated per platform (for example Windows 11 24H2 10.0.26100.8457, Windows 11 25H2 10.0.26200.8457, Windows Server 2022 10.0.20348.5139, Windows Server 2012 R2 6.3.9600.23181) - install the monthly cumulative update that raises the OS to at least the listed build, per https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-33838. Where immediate patching is not possible, the most effective compensating control is to remove or disable the Message Queuing (MSMQ) Windows feature on hosts that do not require it, since the vulnerable code path only exists when MSMQ is installed; the trade-off is that any application relying on MSMQ messaging will break. If MSMQ must stay enabled, restrict which local users can log on to and run code on affected hosts and block untrusted TCP 1801 / MSMQ ports at the host firewall to reduce exposure, accepting that this does not remove the local escalation primitive for users who already have interactive or service access.
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Same weakness CWE-415 – Double Free
View allSame technique Information Disclosure
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External POC / Exploit Code
Leaving vuln.today