EUVD-2026-43911
GHSA-8c98-2wcx-rg4c
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local privilege escalation requiring an existing low-privileged foothold (AV:L/PR:L); the use-after-free race gives AC:H; full SYSTEM compromise yields C:H/I:H/A:H with unchanged scope.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Windows Runtime allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in Microsoft Windows Runtime (WinRT) affects a broad range of Windows client and server builds, from Windows 10 1809 through Windows 11 26H1 and Windows Server 2019 through 2025. An authorized local attacker who can run low-privileged code can trigger a use-after-free memory-corruption condition to elevate to higher privileges, with high confidentiality, integrity, and availability impact implying a path to SYSTEM. No public exploit identified at time of analysis, and the flaw is not on CISA KEV; a vendor patch is available.
Technical ContextAI
The vulnerability lies in Windows Runtime (WinRT), the object-based API layer used pervasively by modern Windows apps and system components across all supported Windows editions. The root cause is CWE-416 (Use After Free): a memory object is freed while a live reference remains, so subsequent access dereferences a dangling pointer. In a component like WinRT - which brokers calls between user-mode apps and privileged system services - an attacker who controls the contents of the reallocated memory can corrupt object state or hijack control flow to run code in a more privileged context. The affected CPE set enumerates Windows 10 (1809/21H2/22H2), Windows 11 (24H2/25H2/26H1), and Windows Server 2019/2022/2025, indicating the vulnerable code is in the shared OS runtime rather than an optional feature.
RemediationAI
Apply the Microsoft security update for CVE-2026-50410 via Windows Update or WSUS/SCCM; the patched build corresponds to the cumulative update for your OS edition as listed in the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50410 (Patch available per vendor advisory - an exact fix build number was not provided in the input, so consult the MSRC page for the KB matching your version). Because exploitation requires local code execution with low privileges, effective compensating controls until patching include restricting who can run code on affected hosts (enforce least privilege and remove unnecessary interactive/local logon rights), applying application allow-listing such as WDAC or AppLocker to limit untrusted binaries, and prioritizing multi-user and server hosts where low-privileged users are present; the trade-off is that allow-listing and logon-right restrictions require tuning and can disrupt legitimate workflows. There is no feature to disable, since WinRT is integral to the OS, so patching is the only complete fix.
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Same weakness CWE-416 – Use After Free
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External POC / Exploit Code
Leaving vuln.today