CVE-2026-102511 in PLC4X
Summary
by MITRE • 09/30/2026
Improper Verification of Source of a Communication Channel in the ADS discovery of the Go implementation of Apache PLC4X (PLC4Go) allows an attacker able to send UDP datagrams to the discovering host to redirect subsequent connections to an arbitrary, attacker-chosen address. The discovery result's connection address was derived from the AmsNetId claimed in the response body rather than from the datagram's actual source address. One spoofed discovery response can therefore insert an inventory entry pointing at any host, including hosts outside the local network, and an application that connects to discovered devices will open its ADS session, including any configured route credentials, to that host.
Additionally, discovery listeners in both implementations can be disabled by a single malformed datagram: - In PLC4Go ADS discovery, a short version block causes a panic that ends the listener for the rest of the discovery call, so legitimate devices answering afterwards are not reported. - In PLC4J, the ADS and EtherNet/IP discoverers stop on an unhandled exception from a malformed response. - The PLC4J Modbus discoverer can be made to spin indefinitely, consuming a CPU core, by a scanned host that sends a partial response.
Exploitation requires the application to invoke the discovery API, which is opt-in, and for the connection redirect, to act on the discovered items.
This issue affects Apache PLC4X: PLC4Go from 0.11.0 before 1.0.0; PLC4J ADS and Modbus drivers from 0.10.0 before 1.0.0; PLC4J EtherNet/IP driver from 0.11.0 before 1.0.0. PLC4Go is consumed as the Go module github.com/apache/plc4x/plc4go; versions refer to the corresponding Apache PLC4X releases.
Users are recommended to upgrade to version 1.0.0, which fixes the issue. Version 1.0.0 derives the connection address from the datagram's source address and logs a warning when the claimed AmsNetId disagrees with it.
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Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified in Apache PLC4X involves critical flaws within the Automatic Device Specification discovery mechanisms of its Go implementation, known as PLC4Go, alongside related issues in the Java implementations including PLC4J. The core issue stems from an improper verification of the source of a communication channel during the ADS discovery process. Specifically, when handling UDP datagrams sent by potential devices on the network, the software incorrectly derives the connection address for subsequent interactions based on the AmsNetId claimed within the response body rather than validating it against the actual IP source address of the incoming packet. This architectural flaw allows an attacker positioned to send UDP datagrams to the discovering host to manipulate the discovery results by injecting spoofed responses that contain arbitrary target addresses. Consequently, any application utilizing this discovery mechanism will establish connections and open ADS sessions with hosts chosen by the attacker rather than legitimate devices on the local network.
The operational impact of this flaw is severe as it facilitates unauthorized access and potential data exfiltration or manipulation within industrial control systems. By redirecting subsequent connections to an arbitrary address, an attacker can intercept sensitive communications or inject malicious commands into the PLC4X session. This redirection includes any configured route credentials associated with the connection, meaning that authentication tokens intended for legitimate devices are instead transmitted to the attacker-controlled host. Furthermore, the vulnerability enables a denial of service scenario through resource exhaustion and discovery disruption. In the Go implementation, sending a single malformed datagram containing a short version block triggers a panic condition that terminates the discovery listener prematurely. This prevents subsequent legitimate device responses from being reported, effectively blinding the scanner to real assets on the network.
Similar reliability issues exist in the Java-based PLC4J implementations which exacerbate the risk of operational disruption. In the ADS and EtherNet/IP discoverers for PLC4J, a single malformed response can cause an unhandled exception that halts the discovery process entirely. This behavior prevents the system from identifying other valid devices on the network segment after encountering the malicious packet. Additionally, the Modbus discoverer in PLC4J is susceptible to infinite loop conditions when processing partial responses from scanned hosts. An attacker exploiting this flaw can force the application to consume a CPU core indefinitely, leading to significant performance degradation or complete unavailability of the discovery service for legitimate operations. These denial of service vectors reduce the reliability and availability of industrial monitoring systems that rely on automated device detection.
From a classification perspective, these vulnerabilities align with CWE-295 Improper Certificate Validation and CWE-807 Reliance on Untrusted Inputs in Security-Critical Decisions, as the system fails to validate the integrity and origin of network data before using it for connection routing. The exploitation path relates to ATT&CK technique T1496 Network Service Scanning where an attacker may use discovery mechanisms to map the environment, but more critically involves MITM or session hijacking concepts due to the redirection of authenticated sessions. Exploitation requires specific conditions: the application must explicitly invoke the opt-in discovery API, and it must act upon the discovered items by attempting to connect to them. This means that passive network observers cannot exploit this flaw directly; active interaction with the vulnerable software is necessary for successful exploitation.
The affected versions include Apache PLC4X PLC4Go from 0.11.0 up to but not including 1.0.0, as well as specific drivers in PLC4J such as ADS and Modbus drivers from 0.10.0 before 1.0.0 and the EtherNet/IP driver from 0.11.0 before 1.0.0. To mitigate these risks, users are strongly advised to upgrade immediately to version 1.0.0 or later. The fixed versions address the source verification flaw by deriving the connection address strictly from the datagram's actual source IP address rather than trusting internal claims like AmsNetId. Additionally, the updated software implements logging warnings when discrepancies arise between claimed identifiers and actual network sources, providing visibility into potential spoofing attempts without allowing automatic redirection to unverified hosts. This ensures that only devices responding from their true network locations are considered for connection establishment, thereby preserving both security and operational integrity in industrial environments.