CVE-2026-111731 in P-Net
Summary
by MITRE • 10/29/2026
P-Net before 1.0.3 enters an infinite loop when handling a read request for the PDPortDataCheck record with subslot 0 (whole module). The loop over the ports never advanced to the next port, so the request never completes and the device stops responding. A remote unauthenticated attacker can use this to cause a denial of service.
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Analysis
by VulDB Data Team • 10/29/2026
The vulnerability identified in P-Net versions prior to 1.0.3 represents a critical logic error within the network protocol implementation that leads to a complete system hang. This flaw specifically manifests when the device processes read requests targeting the PDPortDataCheck record associated with subslot zero, which corresponds to the entire module rather than an individual port. In industrial automation environments where P-Net is commonly deployed for real-time communication between masters and slaves, such stability issues can have severe operational consequences. The root cause lies in a faulty loop structure designed to iterate through available ports during data retrieval operations. Instead of properly incrementing the iterator or advancing to the next port index after processing each entry, the code fails to update its state variable correctly. This oversight results in an infinite loop where the processor remains trapped executing the same block of instructions repeatedly without ever reaching a termination condition or returning control to the main application thread.
From a technical perspective, this defect is classified under CWE-835, which describes loops that do not terminate due to logic errors rather than resource exhaustion typical of buffer overflows. The absence of proper boundary checks and iterator management means that once triggered by a specific input pattern involving subslot zero, the software enters an unrecoverable state. Because P-Net devices often operate in constrained embedded environments with limited processing power and memory, this infinite loop effectively monopolizes CPU resources. Consequently, the device ceases to respond to any further network traffic or internal tasks, leading to a total loss of functionality for that node on the industrial network. This behavior aligns closely with ATT&CK technique T1499, Endpoint Denial of Service, as it involves manipulating system resources to disrupt availability without necessarily compromising confidentiality or integrity.
The operational impact of this vulnerability is significant in production settings where continuous uptime and deterministic response times are mandatory. A remote unauthenticated attacker can exploit this flaw by sending a specifically crafted read request for the PDPortDataCheck record with subslot zero set to trigger the infinite loop condition. Since no authentication is required, the attack surface is broad, allowing any entity on the network segment to initiate the denial of service. The resulting halt in device response disrupts data flow between controllers and field devices, potentially causing production line stoppages, safety system failures, or cascading errors across dependent systems that rely on timely updates from this node. Unlike crashes that might allow for automatic restarts, an infinite loop often requires manual intervention to reset the hardware, increasing downtime and maintenance costs significantly.
Mitigation strategies primarily involve upgrading the P-Net software stack to version 1.0.3 or later, where the developers have addressed the iterator advancement logic within the port handling routine. Until such updates can be applied in a controlled manner, network segmentation should be employed to restrict access to vulnerable devices from untrusted zones. Additionally, implementing strict input validation at gateway levels can help filter out malformed requests targeting specific subslots before they reach the embedded device. Monitoring tools should also be configured to detect abnormal CPU usage patterns or prolonged periods of non-response on P-Net nodes, enabling rapid identification and isolation of affected systems during an active exploitation attempt.