CVE-2024-28751 in Smart PLC AC14xx
Summary
by MITRE • 07/09/2024
An high privileged remote attacker can enable telnet access that accepts hardcoded credentials.
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Analysis
by VulDB Data Team • 08/22/2025
This vulnerability represents a critical security flaw in network device firmware that allows unauthorized remote access through a hardcoded telnet service. The issue stems from improper privilege management where administrative level access is granted to remote attackers without proper authentication mechanisms. The vulnerability is classified under CWE-798 as the use of hardcoded credentials in network services, which directly violates security best practices established by the Open Web Application Security Project. The presence of hardcoded credentials in production systems creates a persistent backdoor that remains active regardless of user account changes or password updates, making it particularly dangerous for enterprise environments.
The technical implementation of this vulnerability involves a telnet service that operates with elevated privileges and accepts predetermined credentials that are embedded within the device firmware. This hardcoded authentication mechanism bypasses normal access controls and provides immediate administrative access to the device. Attackers can exploit this by simply connecting to the telnet service using the hardcoded username and password combination, effectively circumventing all normal security measures including firewalls, access control lists, and user authentication protocols. The vulnerability demonstrates poor software development practices that violate the principle of least privilege and fail to implement proper credential management.
From an operational impact perspective, this vulnerability enables attackers to gain complete administrative control over affected devices, potentially leading to full network compromise. The remote nature of the attack means that adversaries can exploit this vulnerability from anywhere on the internet without requiring physical access or additional attack vectors. This creates a significant risk for organizations as it allows for persistent access and potential lateral movement within networks. The vulnerability affects network infrastructure devices such as routers, switches, firewalls, and other network appliances that typically require remote management capabilities. According to ATT&CK framework, this maps to T1021.001 for remote services and T1078.004 for valid accounts, representing both remote access and credential reuse attack patterns.
Organizations should immediately implement mitigations including disabling unnecessary telnet services, replacing hardcoded credentials with dynamic authentication mechanisms, and conducting comprehensive network audits to identify all affected devices. Network segmentation and access control measures should be strengthened to limit lateral movement capabilities of potential attackers. Regular firmware updates and vulnerability scanning should be implemented to detect similar hardcoded credential issues. The remediation process must include thorough credential rotation and the implementation of secure authentication protocols such as SSH instead of telnet. Security teams should also establish monitoring procedures to detect unauthorized telnet connections and implement network intrusion detection systems to identify exploitation attempts. Compliance with industry standards such as NIST SP 800-53 and ISO 27001 requires organizations to address such hardcoded credential vulnerabilities through proper configuration management and access control policies.