CVE-2011-4861 in Quantum Ethernet Module 140noe77100
Summary
by MITRE
The modbus_125_handler function in the Schneider Electric Quantum Ethernet Module on the NOE 771 device (aka the Quantum 140NOE771* module) allows remote attackers to install arbitrary firmware updates via a MODBUS 125 function code to TCP port 502.
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Analysis
by VulDB Data Team • 01/17/2018
The vulnerability identified as CVE-2011-4861 represents a critical security flaw in Schneider Electric's Quantum Ethernet Module, specifically affecting the NOE 771 device model. This issue resides within the modbus_125_handler function implementation, which processes MODBUS protocol communications on TCP port 502, the standard port for MODBUS TCP/IP communications. The flaw enables remote attackers to execute arbitrary firmware updates on affected devices without proper authentication or authorization, creating a significant attack surface that could compromise industrial control systems.
The technical nature of this vulnerability stems from improper input validation and authentication mechanisms within the MODBUS protocol handler. When the modbus_125_handler function receives a MODBUS function code 125, it fails to properly verify the authenticity of the update request or validate the source of the firmware payload. This weakness directly maps to CWE-284, which addresses inadequate access control mechanisms, and CWE-327, which covers broken or weak cryptographic systems. The function processes the firmware update request without requiring proper credentials or cryptographic verification, making it susceptible to man-in-the-middle attacks or direct exploitation by unauthorized parties.
The operational impact of this vulnerability extends beyond simple remote code execution, as it fundamentally undermines the integrity and availability of industrial control systems. When an attacker successfully installs arbitrary firmware, they can potentially gain persistent control over the device, modify operational parameters, or introduce malicious code that could disrupt industrial processes. This vulnerability particularly affects critical infrastructure environments where Schneider Electric Quantum modules are deployed, including manufacturing facilities, power generation plants, and other industrial automation systems. The attack vector requires only network connectivity to TCP port 502, making it accessible from remote locations without physical access to the device.
Mitigation strategies for this vulnerability must address both immediate security concerns and long-term system hardening. Organizations should implement network segmentation to isolate industrial control systems from general network traffic, utilizing firewalls to restrict access to TCP port 502 to only authorized management systems. Network monitoring should be enhanced to detect unusual MODBUS traffic patterns or unauthorized firmware update attempts. Additionally, the affected devices should be updated with firmware patches provided by Schneider Electric, as these updates typically include proper authentication mechanisms and input validation. Implementing network access control lists and disabling unnecessary services on the affected modules can further reduce the attack surface. From an ATT&CK framework perspective, this vulnerability aligns with techniques such as T1059.005 for remote access and T1547.001 for persistence mechanisms, making it particularly concerning for industrial cybersecurity programs that must defend against sophisticated threats targeting operational technology environments.