CVE-2025-26858 Overview
A buffer overflow vulnerability exists in the Modbus TCP functionality of Socomec DIRIS Digiware M-70 firmware version 1.6.9. This vulnerability allows unauthenticated remote attackers to send specially crafted network packets that can trigger a denial of service condition. The flaw stems from improper input validation (CWE-20) when processing Modbus TCP requests, enabling an attacker to overflow internal buffers and crash the affected device.
Industrial control systems (ICS) and operational technology (OT) environments utilizing Socomec DIRIS Digiware M-70 devices for power monitoring and energy management are particularly at risk. The attack requires no authentication and can be executed remotely over the network, making this a significant threat to critical infrastructure installations.
Critical Impact
Unauthenticated remote attackers can cause denial of service on industrial power monitoring equipment, potentially disrupting critical infrastructure operations and energy management systems.
Affected Products
- Socomec DIRIS Digiware M-70 (Hardware)
- Socomec DIRIS M-70 Firmware version 1.6.9
Discovery Timeline
- 2025-12-01 - CVE-2025-26858 published to NVD
- 2025-12-05 - Last updated in NVD database
Technical Details for CVE-2025-26858
Vulnerability Analysis
This vulnerability affects the Modbus TCP implementation in Socomec DIRIS Digiware M-70 devices running firmware version 1.6.9. The vulnerability has been assigned a CVSS v3.1 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.
Key CVSS metrics indicate:
- Attack Vector (AV): Network - The vulnerability is exploitable remotely
- Attack Complexity (AC): Low - No specialized conditions required
- Privileges Required (PR): None - No authentication needed
- User Interaction (UI): None - No user action required
- Impact: High availability impact with no confidentiality or integrity impact
The EPSS (Exploit Prediction Scoring System) data shows a probability of 0.098% (27th percentile), indicating a relatively moderate likelihood of exploitation in the wild.
Root Cause
The root cause of CVE-2025-26858 is classified as CWE-20 (Improper Input Validation). The Modbus TCP handler in the DIRIS Digiware M-70 firmware fails to properly validate the size and structure of incoming network packets before processing them. When specially crafted packets with malformed or oversized data are received, the firmware attempts to write data beyond allocated buffer boundaries, resulting in memory corruption and device instability.
The Modbus TCP protocol operates on TCP port 502 and is commonly used in industrial environments for communication between SCADA systems, PLCs, and monitoring devices like power meters. The lack of input validation in this implementation allows attackers to craft malicious Modbus requests that exploit the buffer handling weakness.
Attack Vector
The attack is network-based and requires no authentication. An attacker with network access to the vulnerable Modbus TCP service can exploit this vulnerability by sending a sequence of specially crafted packets. The attack flow typically involves:
- Establishing a TCP connection to port 502 on the target device
- Sending malformed Modbus TCP packets with oversized or unexpected data fields
- Triggering the buffer overflow condition in the firmware's packet processing logic
- Causing the device to crash or become unresponsive
The vulnerability affects the availability of the device, potentially disrupting power monitoring and energy management functions in industrial facilities. Since the attack vector is network-based with low complexity and no prerequisites, any attacker with network visibility to the affected device can potentially exploit this vulnerability.
For detailed technical information about the exploitation mechanism, refer to the Cisco Talos vulnerability report (TALOS-2025-2152).
Detection Methods for CVE-2025-26858
Indicators of Compromise
- Unexpected device reboots or unresponsive behavior of DIRIS Digiware M-70 devices
- Abnormal network traffic patterns on TCP port 502 (Modbus TCP)
- Oversized or malformed Modbus TCP requests targeting affected devices
- Multiple connection attempts from unexpected IP addresses to the Modbus service
Detection Strategies
Organizations can implement the following detection strategies to identify potential exploitation attempts:
Network Traffic Analysis: Deploy network monitoring solutions capable of deep packet inspection for Modbus TCP traffic. Look for anomalous packet sizes, malformed function codes, or unusual sequences of requests that deviate from normal operational patterns.
IDS/IPS Signatures: Configure intrusion detection and prevention systems with signatures specific to Modbus protocol anomalies. Rules should flag oversized packets, unexpected data lengths, and rapid connection sequences targeting port 502.
Device Health Monitoring: Implement monitoring for device availability and response times. Sudden unavailability or degraded performance of DIRIS M-70 devices may indicate active exploitation.
Log Analysis: Review network logs for repeated failed connections or unusual traffic volumes to Modbus-enabled devices from untrusted network segments.
Monitoring Recommendations
- Implement network segmentation to isolate ICS/OT networks from general enterprise networks
- Deploy industrial-specific network monitoring tools with Modbus protocol awareness
- Configure alerts for abnormal traffic patterns to TCP port 502
- Maintain baseline network behavior profiles for comparison during incident investigation
- Enable detailed logging on firewalls and network devices at OT network boundaries
How to Mitigate CVE-2025-26858
Immediate Actions Required
- Apply vendor-provided firmware updates as soon as they become available
- Implement network segmentation to restrict access to affected devices from untrusted networks
- Configure firewall rules to limit Modbus TCP (port 502) access to authorized systems only
- Monitor affected devices for signs of exploitation or unexpected behavior
- Review and document all network paths to affected devices
Patch Information
Socomec has published a security advisory addressing this vulnerability. Organizations should consult the official vendor documentation for firmware update availability and installation procedures:
Contact Socomec support for guidance on obtaining and applying the latest firmware version that addresses this vulnerability.
Workarounds
If immediate patching is not possible, implement the following compensating controls:
- Network Isolation: Place affected devices on isolated network segments with strict access controls
- Firewall Rules: Restrict Modbus TCP access to only authorized management stations and SCADA systems
- VPN Requirements: Require VPN connections for any remote access to OT networks containing vulnerable devices
- Disable Unused Services: If Modbus TCP functionality is not required, disable the service on affected devices if possible
# Example firewall rule to restrict Modbus TCP access (iptables)
# Allow Modbus TCP only from authorized SCADA system
iptables -A INPUT -p tcp --dport 502 -s <AUTHORIZED_SCADA_IP> -j ACCEPT
iptables -A INPUT -p tcp --dport 502 -j DROP
# Log blocked Modbus connection attempts
iptables -A INPUT -p tcp --dport 502 -j LOG --log-prefix "MODBUS_BLOCKED: "
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
