CVE-2022-50978: Modbus TCP DOS Vulnerability

CVE-2022-50978 Overview

CVE-2022-50978 is a Missing Authentication for Critical Function vulnerability (CWE-306) that allows an unauthenticated remote attacker to disrupt industrial control system operations by switching between multiple configuration presets via the Modbus TCP protocol. This vulnerability poses significant risks to operational technology (OT) environments where Modbus is commonly used for industrial communications.

Critical Impact

Unauthenticated attackers can remotely disrupt industrial operations by manipulating configuration presets without any authentication, potentially causing denial of service conditions in critical infrastructure systems.

Affected Products

• Industrial control systems utilizing Modbus TCP protocol
• Devices referenced in Innomic security advisory IDS-2026-0001
• Systems exposing Modbus TCP (port 502) to network access

Discovery Timeline

• February 2, 2026 - CVE-2022-50978 published to NVD
• February 3, 2026 - Last updated in NVD database

Technical Details for CVE-2022-50978

Vulnerability Analysis

This vulnerability stems from a fundamental lack of authentication controls on critical Modbus TCP functions. The Modbus protocol, originally designed in 1979 for serial communications, lacks built-in security mechanisms by design. When implemented over TCP/IP without additional authentication layers, it exposes critical configuration functions to any network-accessible attacker.

The vulnerability allows remote attackers to send specially crafted Modbus TCP requests to switch between configuration presets on the target device. Since no authentication is required, an attacker with network access to the Modbus TCP service (typically port 502) can arbitrarily change device configurations, leading to operational disruptions.

The attack requires network-level access but no privileges or user interaction, making it particularly dangerous in environments where Modbus devices are accessible from untrusted network segments.

Root Cause

The root cause is CWE-306: Missing Authentication for Critical Function. The affected system fails to implement proper authentication mechanisms for Modbus TCP commands that control configuration preset switching. This allows any network-connected client to execute privileged operations that should require authentication or authorization verification.

Industrial protocols like Modbus were designed decades ago without security considerations, and many implementations continue to operate without authentication overlays, leaving critical functions exposed to unauthorized access.

Attack Vector

The attack is network-based and can be executed remotely against any system exposing Modbus TCP services. An attacker can exploit this vulnerability by:

1. Identifying systems with exposed Modbus TCP services (typically port 502)
2. Crafting Modbus function code requests to manipulate configuration presets
3. Sending unauthenticated requests to switch between configurations
4. Causing operational disruption through unauthorized configuration changes

The attack requires no user interaction and can be automated at scale against multiple vulnerable devices. Since Modbus lacks encryption, attacks can also be conducted via man-in-the-middle positions on the network.

Detection Methods for CVE-2022-50978

Indicators of Compromise

• Unexpected Modbus TCP traffic on port 502 from unauthorized source IP addresses
• Unusual configuration preset changes in device logs without corresponding authorized maintenance windows
• Modbus function code requests originating from non-standard control system hosts
• Abnormal frequency of configuration modification commands in industrial network traffic

Detection Strategies

• Deploy network intrusion detection systems (IDS) with Modbus protocol analysis capabilities to identify unauthorized configuration commands
• Implement network segmentation monitoring to detect traffic from unauthorized network zones attempting to reach Modbus services
• Configure SIEM rules to correlate configuration change events with authorized change management tickets
• Enable deep packet inspection on industrial firewalls to identify anomalous Modbus function codes

Monitoring Recommendations

• Continuously monitor Modbus TCP traffic patterns for deviation from established baselines
• Log all configuration preset changes and correlate with authorized maintenance schedules
• Implement alerting for Modbus connections from previously unseen IP addresses
• Monitor network flows to identify reconnaissance activity targeting port 502

How to Mitigate CVE-2022-50978

Immediate Actions Required

• Isolate affected Modbus TCP devices behind properly configured industrial firewalls
• Implement network segmentation to restrict Modbus access to authorized control system hosts only
• Deploy allowlisting rules to permit Modbus TCP connections only from known, trusted IP addresses
• Review and audit all systems with Modbus TCP exposure for unauthorized configuration changes

Patch Information

Consult the Innomic CSAF Security Advisory for vendor-specific patch information and remediation guidance. The advisory provides detailed information about affected products and available security updates.

Additional technical details are available in the Innomic CSAF Advisory JSON format for automated security tooling integration.

Workarounds

• Implement network-level access controls using industrial firewalls to restrict Modbus TCP access to authorized control system components only
• Deploy a Modbus security gateway or protocol-aware firewall that can filter unauthorized function codes
• Use VPN tunnels or encrypted overlays for any remote Modbus TCP access requirements
• Consider implementing Modbus/TCP security extensions where supported by the device firmware

# Example firewall configuration to restrict Modbus TCP access
# Allow Modbus TCP only from authorized SCADA hosts
iptables -A INPUT -p tcp --dport 502 -s 10.100.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 502 -j DROP