CVE-2022-50979: Modbus RS485 DOS Vulnerability

CVE-2022-50979 Overview

CVE-2022-50979 is an authentication bypass vulnerability affecting industrial control systems that communicate via Modbus over RS485 serial connections. An unauthenticated attacker with adjacent network access could potentially disrupt operations by switching between multiple configuration presets via Modbus (RS485), leading to denial of service conditions in industrial environments.

Critical Impact

Unauthenticated attackers on adjacent networks can manipulate device configuration presets without authentication, potentially disrupting industrial control system operations.

Affected Products

• Industrial control systems utilizing Modbus RS485 communication (refer to Innomic CSAF Advisory for specific product details)

Discovery Timeline

• 2026-02-02 - CVE CVE-2022-50979 published to NVD
• 2026-02-03 - Last updated in NVD database

Technical Details for CVE-2022-50979

Vulnerability Analysis

This vulnerability is classified under CWE-306 (Missing Authentication for Critical Function). The core issue lies in the lack of authentication mechanisms protecting critical configuration management functions accessible via Modbus protocol over RS485 serial connections.

Modbus is a widely deployed industrial communication protocol that traditionally lacks built-in security features such as authentication or encryption. When critical configuration switching capabilities are exposed via Modbus without additional authentication layers, attackers with physical or logical access to the adjacent network segment can send arbitrary configuration commands to affected devices.

The attack requires adjacent network access, meaning the attacker must be positioned on the same network segment as the target device, typically requiring physical proximity or access to the RS485 serial bus. This limits the attack surface compared to remote network attacks but remains a significant concern in industrial and manufacturing environments where internal network segmentation may be insufficient.

Root Cause

The root cause of this vulnerability is the absence of authentication controls for critical configuration functions exposed through the Modbus RS485 interface. The affected system allows configuration preset switching without verifying the identity or authorization of the requesting party. This represents a fundamental design flaw where security controls were not implemented for sensitive operational functions.

In industrial control systems, configuration presets often control operational parameters that directly impact physical processes. Allowing unauthenticated modification of these settings can result in unexpected system behavior, process disruptions, or safety hazards.

Attack Vector

The attack vector for CVE-2022-50979 requires adjacent network positioning. An attacker must have access to the RS485 serial communication bus or network segment where the vulnerable device operates. From this position, the attacker can craft and transmit Modbus commands to switch configuration presets without providing any authentication credentials.

The attack is characterized by low complexity—once adjacent network access is obtained, exploitation is straightforward. The attacker does not require any prior privileges or user interaction to execute the attack. The primary impact is on system availability, as unauthorized configuration changes can disrupt normal operations.

Exploitation would involve identifying the target device on the Modbus network, determining the function codes and register addresses used for configuration preset management, and transmitting malicious Modbus commands to switch presets. Standard Modbus diagnostic and communication tools could be used to facilitate this attack.

Detection Methods for CVE-2022-50979

Indicators of Compromise

• Unexpected configuration preset changes on Modbus-connected devices without corresponding authorized change requests
• Unusual Modbus traffic patterns or command sequences targeting configuration registers
• Operational anomalies indicating device configuration has been modified

Detection Strategies

• Implement network monitoring on RS485 serial buses to detect unauthorized Modbus traffic
• Deploy industrial protocol deep packet inspection (DPI) solutions capable of analyzing Modbus commands
• Establish baseline profiles for normal Modbus communication patterns and alert on deviations

Monitoring Recommendations

• Monitor and log all configuration changes on affected devices with timestamps and source identification where possible
• Implement alerting for configuration preset changes that occur outside of maintenance windows
• Consider deploying industrial intrusion detection systems (IDS) tuned for Modbus protocol anomalies

How to Mitigate CVE-2022-50979

Immediate Actions Required

• Review the Innomic CSAF Advisory for vendor-specific guidance and patches
• Restrict physical and logical access to RS485 network segments containing vulnerable devices
• Implement network segmentation to isolate industrial control systems from less trusted network zones
• Audit existing Modbus-connected devices for similar authentication bypass vulnerabilities

Patch Information

Refer to the Innomic CSAF Advisory for official patch information and firmware updates. Organizations should prioritize applying vendor-provided patches as they become available and validate that patches address the authentication bypass issue.

Workarounds

• Implement physical access controls to restrict unauthorized access to RS485 serial connections
• Deploy firewall rules or access control lists to limit which devices can communicate via Modbus on the affected network segment
• Consider implementing a Modbus security gateway that adds authentication and authorization capabilities as a compensating control
• Disable or restrict access to configuration preset switching functionality if not operationally required