EUVD-2026-43901
GHSA-7g84-83gr-hw7p
Severity by source
AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Network-triggerable per description (AV:N) but a timing-sensitive UAF race (AC:H) requiring an existing low-privileged account (PR:L); successful EoP yields full C/I/A with scope change (S:C).
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Windows Runtime allows an authorized attacker to elevate privileges over a network.
AnalysisAI
Elevation of privilege in the Windows Runtime (WinRT) component of Windows 11 (24H2, 25H2, 26H1) and Windows Server 2025 allows an authenticated attacker to gain higher privileges by exploiting a use-after-free memory-corruption flaw over the network. Microsoft, who reported the issue, has released a patch; there is no public exploit identified at time of analysis and it is not listed in CISA KEV. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to already hold low-level privileges on the target (CVSS PR:L - an authenticated account or existing foothold) and network reachability to the vulnerable Windows Runtime interface (AV:N), with no user interaction needed (UI:N). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H, score 8.5) signals a serious but conditional threat: network reachable and requiring no user interaction, but needing existing low-level privileges (PR:L) and high attack complexity (AC:H), the latter consistent with the timing/heap-grooming race typical of use-after-free exploitation. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who has already obtained a low-privileged authenticated foothold on, or network access to, a Windows Server 2025 or Windows 11 24H2/25H2/26H1 host sends crafted requests to a WinRT-exposed interface to trigger the use-after-free, grooming the heap to reallocate the freed object under their control. By winning the resulting race condition (reflecting the AC:H rating) they corrupt memory to execute code in a higher-privileged context and, thanks to the scope change, affect resources beyond the initially compromised component. … |
| Remediation | Apply the Microsoft security update for CVE-2026-50340; Patch available per vendor advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50340 - install the corresponding monthly cumulative update (KB) for your specific platform (Windows 11 24H2/25H2/26H1 or Windows Server 2025, including the Server Core KB). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, create an inventory of all Windows 11 and Windows Server 2025 systems currently deployed across your environment, noting which versions are running. …
Sign in for detailed remediation steps and compensating controls.
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External POC / Exploit Code
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