CVE-2026-24790: PLC Authentication Bypass Vulnerability

CVE-2026-24790 Overview

CVE-2026-24790 is a Missing Authentication vulnerability affecting industrial Programmable Logic Controller (PLC) devices. The underlying PLC of the device can be remotely influenced without proper safeguards or authentication, allowing unauthenticated attackers to manipulate critical industrial control system components over the network.

Critical Impact
Remote attackers can manipulate PLC operations without authentication, potentially disrupting industrial processes, modifying control logic, or causing operational safety hazards in critical infrastructure environments.

Affected Products

Welker Industrial PLC Devices (specific versions not disclosed)
Devices referenced in CISA ICS Advisory ICSA-26-050-04

Discovery Timeline

2026-02-20 - CVE-2026-24790 published to NVD
2026-02-20 - Last updated in NVD database

Technical Details for CVE-2026-24790

Vulnerability Analysis

This vulnerability is classified as CWE-306: Missing Authentication for Critical Function. The affected PLC devices lack proper authentication mechanisms for network-accessible interfaces, allowing remote attackers to interact with the PLC without providing valid credentials. This architectural flaw enables unauthorized manipulation of industrial control systems across the network.

The network-accessible nature of this vulnerability means attackers can reach vulnerable devices from remote locations without requiring local access or user interaction. The impact primarily affects the integrity of the system, allowing unauthorized modifications to PLC operations, with secondary availability implications that could disrupt normal industrial processes.

Root Cause

The root cause of CVE-2026-24790 is the absence of authentication controls on the PLC's network interface. Industrial control systems often prioritize operational continuity and ease of access, which can lead to insufficient security controls being implemented. In this case, the PLC accepts commands and configuration changes from any network-connected client without verifying identity or authorization.

Attack Vector

The attack vector is network-based, requiring no authentication, no user interaction, and low complexity to exploit. An attacker with network access to the vulnerable PLC can directly send commands to manipulate the device's operation. This could include:

Modifying PLC ladder logic or control programs
Altering setpoints and operational parameters
Disrupting process control sequences
Reading sensitive configuration data
Stopping or starting PLC operations

The vulnerability is particularly concerning in industrial environments where PLCs control physical processes, as unauthorized manipulation could lead to equipment damage, production disruptions, or safety incidents.

Detection Methods for CVE-2026-24790

Indicators of Compromise

Unexpected network connections to PLC management interfaces from unauthorized IP addresses
Configuration changes to PLC logic or parameters without corresponding authorized change tickets
Anomalous command sequences sent to PLC devices outside normal operational patterns
Network traffic to PLC ports from external or untrusted network segments

Detection Strategies

Deploy network intrusion detection systems (NIDS) with ICS/SCADA protocol awareness to monitor traffic to PLC devices
Implement network segmentation monitoring to detect unauthorized access attempts to OT networks
Enable logging on all network infrastructure devices to capture connection attempts to PLC management interfaces
Use industrial protocol deep packet inspection to identify anomalous or unauthorized PLC commands

Monitoring Recommendations

Establish baseline network traffic patterns for PLC communications and alert on deviations
Monitor for configuration changes on PLC devices using change detection mechanisms
Implement real-time alerting for any connections to PLC devices from non-whitelisted sources
Review access logs regularly for unauthorized access attempts to industrial control systems

How to Mitigate CVE-2026-24790

Immediate Actions Required

Isolate affected PLC devices from untrusted networks immediately using network segmentation
Implement firewall rules to restrict access to PLC management interfaces to authorized IP addresses only
Contact Welker support for vendor-specific guidance and patches
Review the CISA ICS Advisory ICSA-26-050-04 for official mitigation guidance

Patch Information

No specific patch information is currently available in the CVE data. Organizations should monitor the CISA ICS Advisory and vendor communications for firmware updates that address this authentication bypass vulnerability. The GitHub CSAF documentation may contain additional technical details and remediation guidance.

Workarounds

Implement network segmentation to isolate PLC devices on dedicated OT/ICS network segments
Deploy a VPN or jump server architecture requiring authentication before accessing PLC networks
Configure firewall rules to allow only specific, authorized systems to communicate with PLCs
Implement network access control (NAC) to prevent unauthorized devices from connecting to OT networks
Consider deploying an industrial demilitarized zone (IDMZ) architecture between IT and OT networks

bash

# Example firewall rule to restrict PLC access (adapt to your environment)
# Allow only authorized engineering workstation to access PLC
iptables -A INPUT -s 192.168.100.10 -d 192.168.200.50 -p tcp --dport 502 -j ACCEPT
iptables -A INPUT -d 192.168.200.50 -p tcp --dport 502 -j DROP

# Log all connection attempts to PLC networks for monitoring
iptables -A INPUT -d 192.168.200.0/24 -j LOG --log-prefix "PLC_ACCESS: "