Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local use-after-free requiring an existing low-privileged account (AV:L/PR:L), no user interaction, yielding SYSTEM-level control with total C/I/A impact.
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
5DescriptionNVD
Use after free in Windows Backup Engine allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Windows Backup Engine affects a broad range of Windows 10 (21H2, 22H2) and Windows 11 (24H2, 25H2, 26H1) builds, where a use-after-free (CWE-416) lets an already-authenticated local attacker corrupt memory and gain SYSTEM-level control. Microsoft rates it 7.8 (AV:L/PR:L) with total confidentiality, integrity, and availability impact, and a patch is available. There is no public exploit identified at time of analysis and it is not listed in CISA KEV; EPSS is low at 0.25% (16th percentile).
Technical ContextAI
The flaw resides in the Windows Backup Engine, the Microsoft-supplied component responsible for system and file backup operations on Windows client editions. The root cause is CWE-416 Use After Free: the engine references a memory object after it has been freed, allowing an attacker who can influence allocation/free timing to reclaim that memory and manipulate a dangling pointer. Because the Backup Engine runs with elevated (SYSTEM) privilege, controlling the freed object's contents can redirect execution or corrupt service state, converting a low-privilege foothold into full local control. CPE data confirms the affected surface is the base OS across Windows 10 version 21H2/22H2 and Windows 11 version 24H2/25H2/26H1.
RemediationAI
Apply the Microsoft security update; a patch is available per the vendor advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50406. Upgrade to at least the fixed build for your release: Windows 10 21H2 build 10.0.19044.7548, Windows 10 22H2 build 10.0.19045.7548, Windows 11 24H2 build 10.0.26100.8875, Windows 11 25H2 build 10.0.26200.8875, and Windows 11 26H1 build 10.0.28000.2269. Because Microsoft does not expose a standalone toggle for the Backup Engine and exploitation requires an existing local account, the most effective compensating controls until patching are reducing local attack surface: restrict interactive and RDP logon rights to trusted users, enforce least privilege so fewer accounts can execute local code, and monitor for anomalous process activity around backup services; these controls limit who can reach the vulnerable code path but do not remove the flaw, so patching remains the definitive fix.
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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
EUVD-2026-44083
GHSA-c4wh-pp4w-w8fw