CVE-2026-82945 in SOEM
Summary
by MITRE • 10/26/2026
SOEM version 2.0.0 and earlier contains a vulnerability during device configuration where a malicious device can cause memory corruption. The software writes configuration data to a fixed-size array without checking if the array index exceeds its maximum size of EC_MAXFMMU entries. A device presenting more than EC_MAXFMMU configuration blocks can force writes beyond the array boundary, corrupting adjacent memory structures and potentially disrupting subsequent operations.
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Analysis
by VulDB Data Team • 10/26/2026
The vulnerability identified in SOEM versions 2.0.0 and earlier represents a critical buffer overflow flaw within the EtherCAT Open Master implementation during device configuration processes. This security issue stems from an insufficient bounds check when handling Field Management Module (FMMU) entries, which are essential for managing data exchange between the master and slave devices on an EtherCAT network. The software allocates a fixed-size array designated to hold EC_MAXFMMU entries, intending to limit the number of configurable FMMU blocks per device. However, the implementation fails to validate whether the index used to write configuration data remains within the allocated memory boundaries before performing the write operation. This lack of input validation allows an attacker-controlled or maliciously configured slave device to present a sequence of more than EC_MAXFMMU configuration blocks, thereby triggering out-of-bounds writes that corrupt adjacent memory structures.
From a technical perspective, this flaw is classified under CWE-120, Buffer Copy without Checking Size of Input, and specifically manifests as an off-by-one or general buffer overflow depending on the exact offset calculation within the array indexing logic. When a malicious device exceeds the expected limit of configuration blocks, the application writes data past the end of the EC_MAXFMMU array into contiguous memory regions that may contain other critical variables, control structures, or return addresses. This memory corruption can lead to undefined behavior, including segmentation faults, crashes, or potentially arbitrary code execution if an attacker can precisely manipulate the overwritten memory contents. The vulnerability is particularly dangerous in industrial automation environments where EtherCAT networks are often deployed with limited network segmentation and high trust assumptions among connected devices.
The operational impact of this vulnerability extends beyond simple service disruption. In a production environment, such as manufacturing lines or process control systems relying on SOEM for real-time communication, the corruption of memory structures can cause immediate loss of connectivity between the master controller and other legitimate slave devices. This results in unplanned downtime, potential safety hazards if actuators fail to respond correctly due to corrupted state data, and significant financial losses associated with halted production cycles. Furthermore, because EtherCAT is a deterministic real-time protocol, any instability introduced by memory corruption can disrupt timing synchronization across the entire network, leading to cascading failures that are difficult to diagnose without deep forensic analysis of the master application's memory dump.
Mitigation strategies for this vulnerability primarily involve upgrading SOEM to a version where the bounds checking logic has been corrected to strictly enforce the EC_MAXFMMU limit during configuration parsing. Until an updated patch is available, administrators should implement network-level controls such as strict access control lists on EtherCAT segments or utilize industrial firewalls that inspect and filter device configuration requests based on expected parameter limits. Additionally, deploying runtime application self-protection mechanisms or memory safety tools can help detect abnormal memory write patterns indicative of buffer overflows. It is also advisable to isolate critical EtherCAT networks from general IT infrastructure to limit the attack surface available to potential adversaries attempting to exploit this flaw through malicious device injection or compromised slave devices within the network topology.