CVE-2026-55731 in LIP-ME20xC
Summary
by MITRE • 07/24/2026
Unchecked input for loop condition (CWE-606) in the SNMP agent in Loytec LIP-ME201C, L-INX, L-GATE, L-ROC, L-IOB, L-DALI, L-VIS and L-PAD through 8.4.16 on LINX-A64 allows an unauthenticated remote attacker to cause persistent denial of service (CPU exhaustion) via a crafted SNMP GETNEXT request with a large OID component.
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Analysis
by VulDB Data Team • 07/24/2026
This vulnerability represents a critical security flaw in the SNMP agent implementation across multiple Loytec network devices including LIP-ME201C, L-INX, L-GATE, L-ROC, L-IOB, L-DALI, L-VIS and L-PAD models. The issue stems from insufficient input validation within the loop condition handling mechanism where the SNMP agent fails to properly sanitize or limit the length of Object Identifier (OID) components in GETNEXT requests. When an attacker crafts a malicious SNMP request containing an excessively large OID component, the device's SNMP agent processes this unchecked input through a loop that continues until the malformed OID is fully evaluated. This creates a deterministic resource exhaustion scenario where the CPU utilization spikes to 100% as the system becomes trapped in an infinite or extremely prolonged loop. The vulnerability affects firmware versions up to and including 8.4.16 on LINX-A64 platforms, making it particularly concerning given the widespread deployment of these industrial networking devices. This flaw directly maps to CWE-606, which specifically addresses the dangerous practice of using unchecked input in loop conditions, creating a path for denial of service attacks that can persistently consume system resources.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire network infrastructures where these devices serve as critical communication nodes. An unauthenticated remote attacker can exploit this weakness without requiring any credentials or privileged access, making it particularly dangerous in industrial environments where network availability is paramount for operational continuity. The CPU exhaustion attack operates at the protocol level of the SNMP implementation, targeting the fundamental processing loop that handles management requests rather than application-level functions. This means that even if other security controls are in place, the device remains vulnerable to this specific attack vector since it occurs during the initial request parsing phase before any authentication or authorization checks can be performed. The persistent nature of the DoS condition makes it difficult for network administrators to recover without manual intervention, as the affected device continues to consume 100% CPU cycles until rebooted or the problematic SNMP traffic is filtered at the network level.
Mitigation strategies for this vulnerability must address both immediate defensive measures and longer-term architectural improvements. Network administrators should implement SNMP access control lists that filter or block suspicious OID patterns before they reach the vulnerable devices, effectively creating a perimeter defense against this specific attack vector. Additionally, deploying network-based intrusion detection systems capable of identifying and blocking malformed SNMP traffic can provide real-time protection without requiring device-level modifications. The most effective long-term solution involves applying firmware updates from Loytec that implement proper input validation for OID components within loop conditions, ensuring that maximum OID length limits are enforced before processing begins. Organizations should also consider implementing network segmentation strategies to isolate critical industrial control systems from general network traffic, reducing the attack surface and limiting potential impact if other devices in the network become compromised. From an operational security perspective, regular monitoring of device CPU utilization and SNMP traffic patterns can help identify anomalous behavior indicative of exploitation attempts. This vulnerability demonstrates how seemingly minor implementation flaws in standard protocols can create significant security risks, particularly when devices operate in environments where continuous availability is critical for safety and operational requirements. The ATT&CK framework categorizes this as a resource exhaustion technique under the system service manipulation category, emphasizing its potential to disrupt normal operational activities through indirect means rather than direct data compromise.