EUVD-2026-43974
GHSA-cxcw-4f63-5835
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local vector with an existing low-privileged account (AV:L/PR:L), race-condition use-after-free raises complexity (AC:H), and successful elevation yields full C/I/A in an unchanged scope.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Windows App Installer allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in Microsoft Windows App Installer (the AppX/MSIX deployment component) lets a low-privileged but authenticated user corrupt memory via a use-after-free (CWE-416) and gain higher privileges on the host. The flaw affects Windows 11 (23H2, 24H2, 25H2, 26H1) and Windows Server 2025, was reported by Microsoft, and has a vendor patch available. There is no public exploit identified at time of analysis and it is not on CISA KEV, though the CVSS 7.0 rating and full C/I/A impact make it a meaningful patch-cycle priority.
Technical ContextAI
Windows App Installer is the built-in Windows component responsible for installing and managing MSIX/AppX application packages, including handling of the ms-appinstaller: protocol and package deployment operations. The root cause is a use-after-free (CWE-416): a memory object is freed while a dangling reference remains, and subsequent access to that freed object allows an attacker to influence execution or corrupt heap state. When a component running with elevated rights reuses the freed allocation under attacker control, the condition can be steered into privilege escalation rather than a mere crash, which is why the vendor tags also list Denial of Service and Memory Corruption. Per the CPE data the affected code ships in Windows 11 versions 23H2/24H2/25H2/26H1, Windows Server 2025, and Windows Server 2025 Server Core installations.
RemediationAI
Patch available per vendor advisory: apply the Microsoft security update referenced at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-48571 for the affected Windows 11 (23H2/24H2/25H2/26H1) and Windows Server 2025 builds; the MSRC update guide lists the exact fixed KB and build numbers per release, which were not provided in this dataset. Because App Installer can also update through the Microsoft Store, ensure Store/app updates are permitted to deliver the fixed App Installer package where the OS cumulative update does not already cover it. If immediate patching is not possible, reduce exposure by tightening who has interactive/local logon rights on affected hosts (the attack requires an existing low-privileged local account), and consider restricting or disabling MSIX/AppX sideloading and the ms-appinstaller protocol handler via policy where App Installer is not needed - with the trade-off that this can break legitimate app deployment and Store-based installs.
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Same weakness CWE-416 – Use After Free
View allSame technique Denial Of Service
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External POC / Exploit Code
Leaving vuln.today