CVE-2019-6857 in Modicon M580
Summary
by MITRE
A CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability exists in Modicon M580, Modicon M340, Modicon Quantum, Modicon Premium (see security notification for specific versions) which could cause a Denial of Service of the controller when reading specific memory blocks using Modbus TCP.
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Analysis
by VulDB Data Team • 05/29/2026
The vulnerability identified as CVE-2019-6857 represents a critical security flaw affecting several Modicon controller models including the M580, M340, Quantum, and Premium series. This weakness manifests as an improper check for unusual or exceptional conditions, categorized under CWE-754, which fundamentally undermines the robustness of these industrial control systems. The vulnerability specifically impacts Modbus TCP communication protocols when certain memory blocks are accessed, creating a pathway for malicious actors to disrupt critical operations.
The technical implementation of this vulnerability stems from inadequate error handling mechanisms within the Modicon controllers' Modbus TCP stack. When legitimate or malicious requests attempt to read specific memory blocks, the system fails to properly validate exceptional conditions that should trigger graceful error recovery procedures. This improper handling causes the controller to enter an unstable state where normal operational functions become impaired, ultimately leading to a complete denial of service condition that can persist until manual intervention or system reboot occurs.
Operational impact of this vulnerability extends beyond simple service interruption to potentially compromise industrial control processes that depend on these controllers. The denial of service condition can result in production halts, safety system failures, and operational disruptions that may have cascading effects throughout industrial processes. The vulnerability's exploitation requires relatively minimal technical expertise, making it particularly dangerous in environments where physical security measures may be insufficient to prevent unauthorized access to industrial networks. Organizations operating these controllers face significant risk of operational disruption that could result in financial losses, safety hazards, and regulatory compliance issues.
Mitigation strategies for CVE-2019-6857 should prioritize immediate implementation of network segmentation and access controls to limit exposure to unauthorized Modbus TCP communications. Organizations must ensure proper network monitoring and intrusion detection systems are deployed to identify anomalous Modbus traffic patterns that could indicate exploitation attempts. Vendor-supplied firmware updates should be applied promptly to address the root cause of the vulnerability, while operational procedures should include regular system health monitoring and automated alerting for unusual controller behavior. The vulnerability aligns with ATT&CK technique T1499.004 for network denial of service and represents a significant concern for industrial control system security posture, particularly within critical infrastructure sectors where operational continuity is paramount.