CVE-2025-55221 Overview
A denial of service vulnerability exists in the Modbus TCP and Modbus RTU over TCP USB Function functionality of Socomec DIRIS Digiware M-70 firmware version 1.6.9. This high-severity flaw allows an attacker to send specially crafted network packets that can lead to a complete denial of service condition on affected industrial energy monitoring devices. The vulnerability is particularly concerning because it can be triggered by unauthenticated packets sent via Modbus TCP over port 502, requiring no prior authentication or user interaction.
This vulnerability is classified as CWE-306 (Missing Authentication for Critical Function), indicating that the affected Modbus TCP functionality lacks proper authentication mechanisms to validate incoming requests before processing them. The network-based attack vector with low complexity makes this an attractive target for threat actors seeking to disrupt industrial control systems.
Critical Impact
Unauthenticated remote attackers can cause denial of service on Socomec DIRIS Digiware M-70 energy monitoring devices by sending malicious Modbus TCP packets to port 502, potentially disrupting critical industrial energy monitoring operations.
Affected Products
- Socomec DIRIS M-70 Firmware version 1.6.9
- Socomec DIRIS M-70 Hardware
- Industrial environments using Modbus TCP on port 502
Discovery Timeline
- 2025-12-01 - CVE-2025-55221 published to NVD
- 2025-12-05 - Last updated in NVD database
Technical Details for CVE-2025-55221
Vulnerability Analysis
CVE-2025-55221 is a denial of service vulnerability affecting the Modbus TCP and Modbus RTU over TCP USB Function components of the Socomec DIRIS Digiware M-70 energy monitoring device. The vulnerability has been assigned a CVSS 3.1 base score of 7.5 (High) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
The CVSS vector breakdown indicates:
- Attack Vector (AV:N): Network-accessible, meaning remote exploitation is possible
- Attack Complexity (AC:L): Low complexity required for successful exploitation
- Privileges Required (PR:N): No authentication or privileges needed
- User Interaction (UI:N): No user interaction required
- Scope (S:U): Unchanged, impact limited to the vulnerable component
- Confidentiality (C:N): No impact on confidentiality
- Integrity (I:N): No impact on integrity
- Availability (A:H): High impact on availability
The Exploit Prediction Scoring System (EPSS) indicates a probability of approximately 0.057% with a percentile ranking of 17.75, suggesting a relatively low but non-negligible likelihood of exploitation in the wild.
Root Cause
The root cause of this vulnerability is the Missing Authentication for Critical Function (CWE-306). The Modbus TCP implementation in the Socomec DIRIS Digiware M-70 fails to properly authenticate incoming network requests before processing them. This design flaw allows any network-accessible attacker to send malicious packets to the device without first establishing authenticated sessions.
Modbus protocol, by design, was created for closed industrial networks and lacks built-in security mechanisms. When exposed to broader networks or the internet without additional security controls, devices implementing Modbus TCP become vulnerable to various attacks, including this denial of service condition.
Attack Vector
The attack is executed remotely over the network by sending specially crafted packets to the Modbus TCP service listening on port 502. The attack methodology involves:
- Target Identification: The attacker identifies Socomec DIRIS Digiware M-70 devices accessible on the network with Modbus TCP enabled on port 502
- Packet Crafting: A malicious Modbus TCP packet is crafted specifically to trigger the denial of service condition
- Unauthenticated Transmission: The packet is sent without any authentication credentials
- Service Disruption: Upon receiving the malformed packet, the device experiences a denial of service condition, disrupting energy monitoring operations
The vulnerability is specifically triggered through malicious messages sent via Modbus TCP over port 502, making network segmentation and firewall rules critical mitigation controls.
Detection Methods for CVE-2025-55221
Indicators of Compromise
- Unexpected traffic patterns on Modbus TCP port 502 from unauthorized sources
- Device unresponsiveness or frequent restarts of the DIRIS Digiware M-70 units
- Anomalous Modbus TCP packets with unusual function codes or malformed payloads
- Loss of energy monitoring data streams from affected devices
- Network logs showing repeated connection attempts to port 502 from external or unexpected IP addresses
Detection Strategies
Organizations can implement several detection strategies to identify exploitation attempts:
Network-Based Detection: Deploy intrusion detection systems (IDS) with rules specifically designed to monitor Modbus TCP traffic on port 502. Look for packets with anomalous structures, unexpected function codes, or payloads that deviate from normal Modbus communication patterns.
Behavioral Monitoring: Establish baselines for normal Modbus TCP communication patterns and alert on deviations. This includes monitoring for unusual packet sizes, frequencies, and source IP addresses.
Device Health Monitoring: Implement monitoring for device availability and responsiveness. Sudden loss of communication or unexpected device reboots may indicate active exploitation.
SentinelOne Singularity Platform: SentinelOne's network visibility capabilities can help identify anomalous traffic patterns targeting industrial control system protocols. The platform's AI-driven threat detection can correlate suspicious network activity with potential exploitation attempts.
Monitoring Recommendations
- Configure network monitoring tools to alert on any external access attempts to port 502
- Implement Modbus-aware deep packet inspection where feasible
- Monitor device uptime and availability metrics for affected Socomec devices
- Review network flow data for connections to/from DIRIS M-70 devices
- Enable logging on firewalls and network segmentation points protecting ICS networks
- Consider deploying industrial-specific security solutions for enhanced OT visibility
How to Mitigate CVE-2025-55221
Immediate Actions Required
- Restrict network access to Modbus TCP port 502 using firewall rules and network segmentation
- Isolate affected Socomec DIRIS Digiware M-70 devices from untrusted networks
- Audit network access controls to ensure only authorized systems can communicate with affected devices
- Monitor for vendor security updates and patch announcements from Socomec
- Implement network intrusion detection for Modbus TCP traffic anomalies
- Review the Talos Intelligence advisory for additional vendor-specific guidance
Patch Information
As of the last NVD update on 2025-12-05, organizations should consult the Talos Intelligence vulnerability report (TALOS-2025-2251) and Socomec's official channels for the latest patch information and firmware updates. The vulnerability affects firmware version 1.6.9 of the DIRIS Digiware M-70 device.
Organizations are advised to:
- Subscribe to Socomec security advisories
- Monitor the Talos Intelligence report at: https://talosintelligence.com/vulnerability_reports/TALOS-2025-2251
- Plan for firmware updates as they become available
- Test patches in non-production environments before deployment
Workarounds
Until patches are available and deployed, organizations should implement the following workarounds to reduce risk:
Network Segmentation: Place affected devices in isolated network segments with strict access controls. Ensure Modbus TCP traffic on port 502 is only permitted from authorized monitoring and management systems.
Firewall Configuration: Configure firewall rules to block external access to port 502 and limit internal access to known, trusted IP addresses.
VPN Requirements: Require VPN connections for any remote access to networks containing affected devices.
Disable Unnecessary Services: If Modbus TCP functionality is not required, consider disabling the service on affected devices if the configuration permits.
# Example firewall rule to restrict Modbus TCP access (Linux iptables)
# Allow Modbus TCP only from authorized management subnet
iptables -A INPUT -p tcp --dport 502 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 502 -j DROP
# Log denied Modbus TCP connection attempts for monitoring
iptables -A INPUT -p tcp --dport 502 -j LOG --log-prefix "MODBUS_DENIED: "
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
