Windows SMB Client Elevation of Privilege Vulnerability
Plan PatchCVSS 7.8CVE-2026-62799Aug 11, 2026
Microsoft
IT in OT - Windows Server and Active Directory are widely deployed in OT environments
Attack path
Attack VectorLocal
Auth RequiredLow
ComplexityLow
User InteractionNone needed
Summary
Heap-based buffer overflow in Windows SMB Client allows an authorized local attacker to elevate privileges to administrator level on Windows 11 Version 26H1 (x64 and ARM64). Exploitation is assessed as less likely but possible.
What this means
What could happen
An attacker with a local user account could exploit a flaw in Windows SMB Client to gain administrator-level privileges on the system, potentially allowing them to take control of the machine and access sensitive data.
Who's at risk
Organizations running Windows 11 Version 26H1 on x64 or ARM64 systems used for OT workstations, engineering stations, or data historian servers should apply this update. This affects HMI computers, engineering workstations, and any Windows systems managing industrial processes or connected to control networks.
How it could be exploited
An attacker with valid local credentials on a Windows 11 system triggers a heap-based buffer overflow in the SMB Client component through a specially crafted request. This allows privilege escalation from standard user to administrator without further interaction.
Prerequisites
- Local user account credentials
- Access to the affected Windows 11 system
- Windows 11 Version 26H1 (x64 or ARM64)
Local privilege escalationLow complexity attackHeap-based buffer overflow
Exploitability
Unlikely to be exploited — EPSS score 0.3%
Affected products (2)
2 with fix
ProductAffected VersionsFix Status
Remediation & Mitigation
0/1
Schedule — requires maintenance window
0/1Patching may require device reboot — plan for process interruption
HOTFIXUpdate Windows 11 to Build 10.0.28000.2704 or later via the August 2026 security update
CVEs (1)
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