Windows Message Queuing mqac.sys Double Free Local Privilege Escalation
CVE-2026-33838 is a local elevation-of-privilege vulnerability in Microsoft Windows Message Queuing (MSMQ). The flaw is a double free condition in the mqac.sys driver. According to the provided context, the issue stems from failure to validate the existence of an object before performing additional free operations on that object, resulting in a double free. An attacker with the ability to run code locally with low privileges can exploit the flaw without user interaction. Successful exploitation can lead to arbitrary code execution in kernel context and elevation to SYSTEM.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
The version that knows your environment.
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.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.