CVE-2026-22924: SIMATIC CN 4100 DoS Vulnerability

CVE-2026-22924 Overview

CVE-2026-22924 affects Siemens SIMATIC CN 4100 devices running firmware versions earlier than V5.0. The vulnerability stems from missing authentication for a critical function [CWE-306], allowing unauthenticated network attackers to open connections to the device without restriction. This exposure enables resource exhaustion conditions that can disrupt normal device operations. Attackers can also leverage the lack of authentication to perform unauthorized actions, impacting both the integrity and availability of the affected industrial control system. Siemens disclosed the issue in advisory SSA-032379. The SIMATIC CN 4100 is an industrial communication node used in operational technology (OT) environments, making this vulnerability particularly relevant for industrial network operators.

Critical Impact

Unauthenticated network attackers can exhaust resources and perform unauthorized actions on SIMATIC CN 4100 devices, disrupting industrial operations.

Affected Products

• Siemens SIMATIC CN 4100 (all versions prior to V5.0)
• Industrial control system deployments using SIMATIC CN 4100 communication nodes
• OT networks exposing SIMATIC CN 4100 management interfaces

Discovery Timeline

• 2026-05-12 - CVE-2026-22924 published to NVD
• 2026-05-12 - Last updated in NVD database

Technical Details for CVE-2026-22924

Vulnerability Analysis

The vulnerability resides in the SIMATIC CN 4100 application's network connection handling logic. The application accepts incoming connections without enforcing authentication checks on the connecting client. An attacker with network reachability to the device can establish multiple unauthenticated sessions and consume finite system resources such as connection slots, memory, or processing threads.

The weakness is classified under CWE-306 (Missing Authentication for Critical Function). The CVSS 4.0 vector indicates network-accessible exploitation with no privileges or user interaction required, producing high impact on integrity and availability while confidentiality remains unaffected. The EPSS probability is 0.039% at the 11.689 percentile, reflecting low observed exploitation activity at present.

Root Cause

The root cause is the absence of authentication enforcement before the application processes connection requests. Without an authentication gate, the device cannot distinguish legitimate operators from anonymous attackers, allowing arbitrary clients to consume resources and invoke functions intended for authorized users.

Attack Vector

An attacker reaches the device over the network and opens repeated or long-lived unauthenticated connections. Sustained connection volume exhausts system resources, degrading availability for legitimate control traffic. The same unauthenticated access path permits unauthorized actions that affect device integrity, including operations that should require operator credentials.

No verified exploit code is publicly available. Refer to the Siemens
Security Advisory SSA-032379 for technical details on the affected
connection handling logic.

Detection Methods for CVE-2026-22924

Indicators of Compromise

• Unusual volume of inbound TCP connections to SIMATIC CN 4100 management ports from unexpected source addresses
• Device performance degradation, dropped sessions, or unresponsive management interfaces on SIMATIC CN 4100 nodes
• Log entries showing repeated connection attempts without successful authentication handshakes

Detection Strategies

• Deploy network intrusion detection signatures that flag high-rate connection patterns toward SIMATIC CN 4100 IP addresses
• Baseline normal operator traffic to the device and alert on deviations in connection count, source diversity, or session duration
• Inspect OT network segments for traffic originating outside authorized engineering workstations or jump hosts

Monitoring Recommendations

• Forward SIMATIC CN 4100 syslog and connection telemetry to a central SIEM for correlation with broader OT events
• Monitor north-south traffic between IT and OT zones for unauthorized flows targeting SIMATIC management protocols
• Track device CPU, memory, and connection table utilization to identify early signs of resource exhaustion

How to Mitigate CVE-2026-22924

Immediate Actions Required

• Upgrade SIMATIC CN 4100 firmware to version V5.0 or later as released by Siemens
• Restrict network access to the SIMATIC CN 4100 management interfaces to trusted engineering workstations only
• Place affected devices behind a properly configured industrial firewall enforcing source-based access control

Patch Information

Siemens addresses CVE-2026-22924 in SIMATIC CN 4100 firmware V5.0. Operators should review the Siemens Security Advisory SSA-032379 for upgrade procedures, version verification steps, and any device-specific guidance before deploying the fix in production environments.

Workarounds

• Apply network segmentation to isolate SIMATIC CN 4100 devices within a dedicated OT VLAN with strict ingress filtering
• Enforce allowlists at the firewall to permit connections only from authorized engineering hosts and management servers
• Disable or block exposure of management services to any untrusted network until firmware V5.0 is deployed

# Example firewall allowlist (adapt to your environment)
# Permit only the engineering workstation to reach the SIMATIC CN 4100
iptables -A FORWARD -s 10.10.20.5 -d 10.20.30.10 -p tcp -j ACCEPT
iptables -A FORWARD -d 10.20.30.10 -j DROP