CVE-2004-0432 in ProFTPD
Summary
by MITRE
ProFTPD 1.2.9 treats the Allow and Deny directives for CIDR based ACL entries as if they were AllowAll, which could allow FTP clients to bypass intended access restrictions.
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Analysis
by VulDB Data Team • 07/12/2025
The vulnerability identified as CVE-2004-0432 represents a critical access control flaw in ProFTPD version 1.2.9 that fundamentally undermines the security of file transfer operations. This issue stems from the improper handling of CIDR (Classless Inter-Domain Routing) based access control list entries within the FTP server configuration. When administrators configure access restrictions using CIDR notation for Allow and Deny directives, the software fails to properly interpret these network address ranges, instead treating them as if all connections were explicitly allowed. This misinterpretation creates a dangerous security gap where unauthorized FTP clients can bypass intended access restrictions and gain access to protected resources.
The technical root cause of this vulnerability lies in the flawed parsing and evaluation of CIDR network address specifications within ProFTPD's access control mechanism. When the server encounters CIDR-based entries in the Allow or Deny directives, it does not correctly process the subnet mask portions of the address ranges. This results in the access control system defaulting to an "allow all" behavior rather than properly enforcing the intended network-based restrictions. The flaw manifests specifically when administrators attempt to configure granular access controls based on IP address ranges, which is a common practice in network security management. This misconfiguration allows attackers to exploit the system by connecting from IP addresses that fall within the incorrectly interpreted CIDR ranges, effectively circumventing the intended access controls.
The operational impact of this vulnerability extends beyond simple unauthorized access, creating potential risks for data confidentiality and system integrity within organizations relying on ProFTPD for file transfer services. Attackers can exploit this weakness to gain access to restricted directories, potentially leading to data breaches, unauthorized file modifications, or even system compromise through further exploitation. The vulnerability affects the fundamental security model of the FTP server, as it undermines the principle of least privilege that administrators rely on to control access to sensitive resources. Organizations using ProFTPD with CIDR-based access controls are particularly at risk, as the flaw can allow attackers to bypass multiple layers of network security that were intended to protect critical file transfer operations.
The vulnerability aligns with CWE-284, which addresses improper access control in software systems, and demonstrates how configuration management flaws can create significant security weaknesses in network services. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation and initial access tactics, as attackers can leverage the flaw to gain unauthorized access to the FTP server and potentially move laterally within the network. Organizations should immediately implement mitigations including upgrading to a patched version of ProFTPD, reviewing all CIDR-based access controls to ensure proper configuration, and implementing additional network-level controls such as firewall rules to restrict FTP access at the network boundary. The recommended remediation involves not only updating the software but also conducting thorough security audits of all FTP server configurations to identify and correct similar access control misconfigurations that could potentially exist in other network services or applications.