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CVE-2026-33838 is a local elevation-of-privilege vulnerability in Microsoft Windows Message Queuing (MSMQ). The flaw is a double-free memory corruption issue, classified as CWE-415, and has been described as occurring within the mqac.sys driver. The vulnerable condition stems from improper handling of object lifetime, where the implementation can perform additional free operations on an object whose existence has not been properly validated. An authenticated local attacker with the ability to execute low-privileged code on a system where MSMQ is installed and enabled can exploit the flaw to elevate privileges. Available reporting indicates successful exploitation may result in arbitrary code execution in kernel context, which in turn enables escalation to SYSTEM on the affected host.
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No public exploit code observed for this vulnerability.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
4 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A local elevation of privilege vulnerability in Windows Message Queuing (MSMQ) caused by a double free condition, allowing an authorized attacker with low privileges to gain SYSTEM privileges.
A local privilege escalation vulnerability caused by a double free memory corruption flaw in the Windows Message Queuing (MSMQ) service that can allow an authenticated local user to gain SYSTEM privileges.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.