CVE-2026-4769 in System IO Field
Summary
by MITRE • 07/13/2026
Certain devices in the WAGO System I/O Field series activate an internal diagnostic capability during the initial startup sequence. This functionality is not formally documented and becomes accessible without authentication for a brief period in the early boot phase. During this window, an unauthenticated remote attacker can gain access to the internal system processes, resulting in full system compromise.
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Analysis
by VulDB Data Team • 07/13/2026
The vulnerability described affects WAGO System I/O Field series devices where an undocumented internal diagnostic capability is activated during the initial startup sequence. This diagnostic functionality becomes accessible without authentication during a brief window in the early boot phase, creating a significant security weakness that can be exploited by unauthenticated remote attackers. The lack of proper access controls during this critical initialization period represents a fundamental flaw in the device's security architecture.
This vulnerability stems from improper implementation of security mechanisms during system initialization, where the diagnostic features should remain restricted to authorized personnel but instead become publicly accessible. The timing of this exposure during the boot sequence is particularly concerning because it occurs before normal authentication processes are fully established and operational. According to CWE-284, this represents an improper access control vulnerability where the system grants unauthorized access to privileged functions during a critical phase of operation.
The operational impact of this vulnerability is severe as it allows full system compromise without any prior authentication requirements. An attacker can exploit this window to gain access to internal system processes, potentially enabling complete control over the device's operations and data handling capabilities. This level of access could facilitate further attacks within connected networks, data exfiltration, or disruption of industrial control systems that rely on these field devices for operational integrity.
The attack surface is particularly concerning in industrial environments where WAGO devices are commonly deployed for process control and monitoring applications. The lack of proper authentication during boot sequences creates an opportunity for attackers to manipulate system behavior before normal security controls are active. This vulnerability aligns with ATT&CK technique T1059 which involves executing malicious code through legitimate system processes, and T1210 which targets remote access to systems through unsecured entry points.
Mitigation strategies should include implementing proper authentication mechanisms during the boot phase, ensuring that diagnostic capabilities remain restricted even during initialization sequences. Device manufacturers should document all system behaviors and implement secure boot processes that prevent unauthorized access to internal functions. Network segmentation and monitoring of unusual access patterns during boot phases can also help detect potential exploitation attempts. Regular firmware updates should address this vulnerability by strengthening authentication requirements throughout the entire system startup process, ensuring that no unauthenticated access windows exist for privileged system functionality.