CVE-2003-0135 in Linux
Summary
by MITRE
vsftpd FTP daemon in Red Hat Linux 9 is not compiled against TCP wrappers (tcp_wrappers) but is installed as a standalone service, which inadvertently prevents vsftpd from restricting access as intended.
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Analysis
by VulDB Data Team • 04/14/2019
The vulnerability described in CVE-2003-0135 pertains to the vsftpd FTP daemon implementation within Red Hat Linux 9 operating systems. This issue represents a fundamental flaw in the service configuration and compilation process that undermines the intended security controls for network access management. The vsftpd daemon, which serves as a secure file transfer protocol server, was installed without proper integration with TCP wrappers, a critical security framework designed to control network access to services based on host-based access control mechanisms.
The technical root cause of this vulnerability lies in the compilation and installation process of the vsftpd service where the daemon was built without linking against the tcp_wrappers library. This omission creates a significant security gap because TCP wrappers provide a robust mechanism for controlling access to network services through the use of access control lists and host-based filtering. When a service is compiled without TCP wrapper support, it cannot utilize the standard host-based access control features that are typically available through the /etc/hosts.allow and /etc/hosts.deny configuration files. The vulnerability specifically manifests when vsftpd operates as a standalone service without proper integration with the TCP wrapper framework, which is a common deployment pattern in many Linux distributions.
The operational impact of this vulnerability is substantial as it allows unauthorized access to FTP services that should be restricted based on host-based access control policies. Attackers can potentially exploit this weakness to gain access to FTP servers without being subject to the intended access restrictions that would normally be enforced by TCP wrappers. This creates a scenario where the FTP service becomes vulnerable to unauthorized connections from any host that can reach the service, effectively bypassing the intended network security controls. The vulnerability directly affects the principle of least privilege and access control enforcement, as the service cannot properly implement host-based restrictions that are fundamental to network security architectures. This issue represents a classic case of incomplete security implementation where the service fails to leverage existing security infrastructure.
From a cybersecurity perspective, this vulnerability aligns with CWE-692, which describes incomplete protection mechanisms that fail to provide the expected level of security control. The issue also relates to ATT&CK technique T1190, which involves exploiting vulnerabilities in network services to gain unauthorized access to systems. Organizations deploying vsftpd services without proper TCP wrapper integration face significant risks including unauthorized file access, potential data breaches, and compromised system integrity. The vulnerability demonstrates how seemingly minor compilation or configuration issues can create substantial security weaknesses that directly impact the security posture of network services. Mitigation strategies should include recompiling the vsftpd daemon with proper TCP wrapper support, implementing alternative access control mechanisms such as firewall rules, and ensuring that network services are properly configured to enforce access restrictions. System administrators should also consider implementing additional security controls including intrusion detection systems, regular security audits, and proper network segmentation to reduce the attack surface and limit the potential impact of such vulnerabilities.
The broader implications of this vulnerability extend beyond the immediate security concerns to highlight the importance of proper service configuration and security framework integration. This issue underscores the critical need for comprehensive security testing during software deployment and the importance of ensuring that security controls are properly implemented and functioning as intended. Organizations should establish robust security configuration management processes that include verification of security controls and proper integration of security frameworks to prevent similar issues from occurring in other network services and applications.