CVE-2017-7898 in MicroLogix 1100
Summary
by MITRE
An Improper Restriction of Excessive Authentication Attempts 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. There are no penalties for repeatedly entering incorrect passwords.
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Analysis
by VulDB Data Team • 06/03/2026
The vulnerability described in CVE-2017-7898 represents a critical weakness in authentication mechanisms within Rockwell Automation Allen-Bradley MicroLogix series programmable logic controllers. This issue affects multiple models including both 1100 and 1400 series controllers, specifically those with firmware versions 16.00 and earlier. The fundamental problem lies in the complete absence of account lockout or rate limiting mechanisms that would normally prevent brute force authentication attacks. These industrial control systems operate within critical infrastructure environments where unauthorized access could lead to significant operational disruptions or safety hazards.
The technical flaw manifests as a complete lack of enforcement for authentication attempt limits, creating an environment where malicious actors can continuously attempt password guesses without facing any form of account lockout or temporary access denial. This vulnerability directly maps to CWE-307 - "Improper Restriction of Excessive Authentication Attempts" which specifically addresses the absence of mechanisms to prevent automated password guessing attacks. The vulnerability affects both Series A and B variants of the affected controllers, indicating a systemic design flaw rather than an isolated implementation error.
From an operational standpoint, this vulnerability creates substantial risk for industrial environments that rely on these controllers for process automation and control. The absence of authentication attempt restrictions means that an attacker with network access could potentially perform unlimited password guessing attempts, leading to unauthorized system access and potential compromise of critical manufacturing processes. This weakness particularly impacts the confidentiality, integrity, and availability aspects of the industrial control systems as defined by the NIST Cybersecurity Framework. The vulnerability could be exploited by attackers to gain administrative access to control systems, potentially leading to production disruptions, safety hazards, or data manipulation.
The impact of this vulnerability extends beyond simple unauthorized access as it creates opportunities for attackers to perform lateral movement within industrial networks, potentially accessing other connected systems. This aligns with ATT&CK technique T1078 - Valid Accounts, where adversaries leverage legitimate credentials to maintain access to systems. Organizations should implement network segmentation and access controls to limit exposure, while also considering firmware updates when available. The lack of automatic account lockout mechanisms represents a fundamental security design flaw that requires immediate attention, as these controllers are often deployed in environments where physical security is already compromised or insufficient. The vulnerability underscores the importance of implementing proper authentication policies even in industrial control environments where traditional security measures may be insufficient or absent.