CVE-2017-7903 in MicroLogix 1100
Summary
by MITRE
A Weak Password Requirements issue was discovered in Rockwell Automation Allen-Bradley MicroLogix 1100 programmable-logic controllers 1763-L16AWA, Series A and B, Version 16.00 and prior versions; 1763-L16BBB, Series A and B, Version 16.00 and prior versions; 1763-L16BWA, Series A and B, Version 16.00 and prior versions; and 1763-L16DWD, Series A and B, Version 16.00 and prior versions and Allen-Bradley MicroLogix 1400 programmable logic controllers 1766-L32AWA, Series A and B, Version 16.00 and prior versions; 1766-L32BWA, Series A and B, Version 16.00 and prior versions; 1766-L32BWAA, Series A and B, Version 16.00 and prior versions; 1766-L32BXB, Series A and B, Version 16.00 and prior versions; 1766-L32BXBA, Series A and B, Version 16.00 and prior versions; and 1766-L32AWAA, Series A and B, Version 16.00 and prior versions. The affected products use a numeric password with a small maximum character size for the password.
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Analysis
by VulDB Data Team • 06/03/2026
The vulnerability identified as CVE-2017-7903 represents a critical weakness in industrial control systems specifically affecting Rockwell Automation Allen-Bradley MicroLogix series programmable logic controllers. This weakness stems from insufficient password requirements that allow attackers to exploit weak authentication mechanisms within these industrial devices. The affected models span multiple variants of both MicroLogix 1100 and 1400 series controllers, all running firmware versions 16.00 and earlier, making this a widespread issue across numerous industrial installations. The vulnerability specifically targets the authentication framework of these controllers, which are commonly deployed in manufacturing environments, process control systems, and other critical infrastructure applications where security is paramount.
The technical flaw manifests in the implementation of password policies that permit only numeric passwords with limited character lengths, typically restricting users to short numerical sequences. This design flaw creates a significant attack surface as numeric-only passwords with small maximum character sizes are inherently vulnerable to brute force attacks and dictionary attacks. The weakness directly maps to CWE-521 Weak Password Requirements, which classifies inadequate password strength criteria as a fundamental security vulnerability. Attackers can exploit this weakness by systematically testing common numeric patterns, making the authentication process trivial to compromise. The limited character set combined with small maximum password lengths significantly reduces the entropy of the authentication mechanism, effectively creating a predictable and easily guessable security barrier.
The operational impact of this vulnerability extends beyond simple unauthorized access, as these controllers manage critical industrial processes and machinery. An attacker who successfully exploits this weakness gains full administrative access to the affected controllers, potentially allowing them to modify program logic, alter process parameters, or disrupt production operations. This compromise can lead to significant financial losses, safety hazards, and operational disruptions in manufacturing environments. The vulnerability is particularly concerning in the context of industrial control systems where the integrity of process control is essential for safety and operational continuity. Organizations using these controllers may face unauthorized modifications to production processes, data manipulation, or complete system compromise that could affect entire production lines or facility operations.
Mitigation strategies for this vulnerability require immediate attention from industrial organizations and system administrators. The primary recommendation involves upgrading affected controllers to firmware versions that address the weak password requirements, ensuring that password policies enforce sufficient complexity with minimum length requirements and support mixed character sets. Network segmentation and access controls should be implemented to limit physical and network access to these controllers, reducing the attack surface available to potential adversaries. Additionally, organizations should implement monitoring solutions to detect unauthorized access attempts and establish regular security assessments of their industrial control systems. The mitigation approach should align with industrial security frameworks such as NIST SP 800-82 and IEC 62443 standards, which emphasize the importance of strong authentication mechanisms and secure configuration management in industrial environments. Regular security training for personnel managing these systems is also crucial to ensure proper password management practices and awareness of potential social engineering attacks that could exploit this vulnerability.