CVE-2026-1876 in MELSEC iQ-F FX5-ENET IP Ethernet Module FX5-ENET
Summary
by MITRE • 03/03/2026
Improper Resource Shutdown or Release vulnerability in Mitsubishi Electric Corporation MELSEC iQ-F Series FX5-ENET/IP Ethernet Module FX5-ENET/IP all versions allows a remote attacker to cause a denial-of-service (DoS) condition on the products by continuously sending UDP packets to the products. A system reset of the product is required for recovery.
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Analysis
by VulDB Data Team • 05/05/2026
The CVE-2026-1876 vulnerability represents a critical improper resource shutdown or release flaw within Mitsubishi Electric Corporation's MELSEC iQ-F Series FX5-ENET/IP Ethernet Module. This vulnerability resides in the network communication handling mechanisms of the FX5-ENET/IP module, which serves as a crucial component in industrial automation systems. The issue manifests when the device fails to properly manage and release network resources during continuous UDP packet transmission, leading to resource exhaustion and subsequent system instability. The vulnerability is particularly concerning as it affects all versions of the FX5-ENET/IP module, indicating a fundamental design flaw rather than a specific implementation error that might have been patched in later releases.
The technical exploitation of this vulnerability occurs through continuous UDP packet flooding targeting the affected Ethernet module. When the module receives sustained UDP traffic, it fails to properly terminate or release network connections and associated resources, causing progressive resource depletion. This improper resource management creates a condition where the system's network stack becomes overwhelmed, leading to complete service unavailability. The vulnerability directly maps to CWE-404, which describes improper resource shutdown or release, and aligns with ATT&CK technique T1499.1 for network denial of service attacks. The flaw essentially creates a resource leak scenario where network buffers, connection tracking structures, and other system resources gradually become consumed until the system reaches a state where it can no longer process legitimate network traffic.
From an operational impact perspective, this vulnerability poses significant risks to industrial control systems and manufacturing environments where the FX5-ENET/IP module operates as a core communication component. The requirement for system reset to recover from the denial-of-service condition creates substantial operational disruption, potentially leading to production downtime, safety system degradation, and increased maintenance overhead. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the operational network boundary, making it particularly dangerous for connected industrial environments. Organizations relying on these modules for critical automation processes face potential cascading effects where a successful DoS attack on a single module could impact entire production lines or facility operations. The vulnerability's impact extends beyond immediate service disruption to include potential safety implications in environments where network reliability is paramount for operational continuity.
Mitigation strategies for CVE-2026-1876 should focus on both network-level protections and operational procedures. Network segmentation and access control measures should be implemented to restrict unauthorized access to the affected Ethernet modules, while firewall rules can be configured to limit UDP traffic to essential ports only. The implementation of rate limiting and connection tracking mechanisms at the network perimeter can help prevent the sustained packet flooding that triggers the vulnerability. Device-level mitigations include regular firmware updates when available, though the universal nature of this vulnerability across all versions suggests that comprehensive fixes may be required. Operational procedures should include monitoring for unusual network traffic patterns and implementing automated alerting systems to detect potential exploitation attempts. Additionally, organizations should consider network isolation of critical control systems and implement redundant communication paths to minimize the impact of potential DoS conditions. The vulnerability underscores the importance of secure network design principles and proper resource management in industrial control systems, aligning with NIST SP 800-82 guidelines for industrial control system security.