Windows SMB Server Denial of Service Vulnerability
Plan PatchCVSS 7.5CVE-2026-70133Oct 13, 2026
Microsoft
IT in OT - Windows Server and Active Directory are widely deployed in OT environments
Attack path
Attack VectorNetwork
Auth RequiredNone
ComplexityLow
User InteractionNone needed
Summary
Windows SMB Server does not properly limit or throttle resource allocation, allowing an attacker to send crafted network requests that exhaust server resources and cause a denial of service. Any Windows system running SMB Server is affected.
What this means
What could happen
An attacker on your network could send malicious SMB requests to crash or freeze Windows servers and computers, disrupting operations until the system reboots or recovers.
Who's at risk
Water authorities and utilities running Windows-based SCADA servers, historian systems, or administrative workstations connected to control networks. Primary concern is Windows Server 2019 and 2022 systems used for data logging, reporting, or as gateways between control networks and enterprise IT.
How it could be exploited
An attacker with network access to port 445 (SMB) sends specially crafted requests that trigger unbounded resource consumption on the target system. No credentials or user interaction are required; the attacker can target any reachable Windows device running SMB Server.
Prerequisites
- Network access to port 445 (SMB)
- No authentication required
remotely exploitableno authentication requiredlow complexity
Exploitability
Some exploitation risk — EPSS score 1.1%
Affected products (28)
28 with fix
ProductAffected VersionsFix Status
Remediation & Mitigation
0/3
Do now
0/1WORKAROUNDRestrict SMB (port 445) network access at your firewall to only authorized internal networks and administrative systems. Block all SMB traffic from untrusted or external networks.
Schedule — requires maintenance window
0/1Patching may require device reboot — plan for process interruption
Windows Server 2019
HOTFIXApply the October 2026 Windows security update to all affected systems. For Windows Server 2022, update to Build 10.0.20348.5761 or later. For Windows Server 2019, update to Build 10.0.17763.9376 or later. For Windows 10/11, update to the corresponding build number listed for your version.
Long-term hardening
0/1HARDENINGDisable or disable SMB v1 protocol on all systems that do not require it, as older protocol versions may be more vulnerable. Use Group Policy or Windows Defender Firewall to enforce this.
CVEs (1)
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