EUVD-2026-43847
GHSA-3p26-p878-mh93
Severity by source
AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Local link-following EoP needs an authenticated low-priv user (PR:L) and a privileged backup action to trigger it (UI:R); full C/I/A as it yields SYSTEM.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Improper link resolution before file access ('link following') in Windows Server Backup allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in Windows Server Backup (WBADMIN component shipped with Windows 10 21H2/22H2 and Windows 11 24H2/25H2/26H1) lets an authorized, low-privileged user abuse a symbolic-link/junction race so that a backup operation acts on an attacker-chosen path, yielding SYSTEM-level access. Microsoft has released a patch and reported the flaw itself; there is no public exploit identified at time of analysis and it is not listed in CISA KEV. Successful exploitation requires local access plus user interaction, which lowers the realistic threat relative to the 7.3 base score.
Technical ContextAI
The weakness is CWE-59 (Improper Link Resolution Before File Access, or 'link following'). Windows Server Backup runs privileged file operations, and when it resolves a path it can be tricked into following an NTFS symbolic link, junction, or hard link that a low-privileged user has planted. Because the backup service dereferences the link while operating with elevated rights, the attacker redirects a trusted write/read to a location the attacker could not otherwise touch. The CPE data shows the affected surface is the OS-bundled backup feature across current Windows 10 and Windows 11 servicing branches (21H2, 22H2, 24H2, 25H2, 26H1) rather than a standalone server product, indicating the vulnerable code lives in the in-box backup binaries/service.
RemediationAI
Patch available per vendor advisory: apply the Microsoft cumulative update that addresses CVE-2026-50364 for your specific Windows 10/11 servicing branch, using the KB listed at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50364 (exact fixed build not restated in the provided data - pull it from the MSRC page per branch). Until patched, reduce exposure by limiting who can run or schedule Windows Backup operations and by restricting standard users' ability to create symbolic links/junctions - the SeCreateSymbolicLinkPrivilege is admin-only by default, so verify it has not been granted to non-admins (trade-off: minimal, since most workloads do not need it). Where the built-in backup feature is unused, disabling the Windows Server Backup role/feature removes the attack surface entirely (trade-off: loss of native backup capability, so ensure an alternative backup solution is in place). Standard EoP hygiene - avoiding running backup jobs while untrusted local users are active on the host - also limits the required user-interaction trigger.
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Same weakness CWE-59 – Improper Link Resolution Before File Access
View allSame technique Information Disclosure
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External POC / Exploit Code
Leaving vuln.today