CVE-2001-0794 in Anonymous FTP Server
Summary
by MITRE
Buffer overflow in A-FTP Anonymous FTP Server allows remote attackers to cause a denial of service via a long USER command.
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Analysis
by VulDB Data Team • 04/10/2019
The vulnerability identified as CVE-2001-0794 represents a critical buffer overflow flaw within the A-FTP Anonymous FTP Server implementation that exposes systems to remote exploitation. This vulnerability specifically manifests when the server processes a USER command containing excessive input data, creating a condition where memory boundaries are exceeded and potentially leading to system instability or complete service disruption. The flaw resides in the server's input validation mechanisms, which fail to properly sanitize or limit the length of user-provided authentication credentials during the initial connection phase.
From a technical perspective this buffer overflow occurs at the application layer within the FTP protocol handling code where the server allocates a fixed-size buffer to store user credentials. When an attacker submits a USER command with data exceeding the allocated buffer size, the excess data overflows into adjacent memory regions, potentially corrupting critical program state information or executing arbitrary code. The vulnerability is classified as a classic stack-based buffer overflow according to CWE-121, which falls under the broader category of CWE-787 - "Out-of-bounds Write" and represents a fundamental flaw in memory management practices within the server application. The attack vector requires no authentication and can be executed remotely, making it particularly dangerous as it allows unauthenticated adversaries to exploit the service without requiring any prior access credentials.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can potentially lead to complete system compromise or unauthorized access to sensitive data repositories. When the buffer overflow occurs during the USER command processing, the server may crash or become unresponsive, effectively preventing legitimate users from accessing the FTP service. In more severe cases, if the overflow is carefully crafted, it could allow attackers to execute malicious code with the privileges of the FTP service account, potentially leading to full system compromise. The vulnerability affects organizations that rely on legacy FTP implementations and demonstrates the critical importance of proper input validation and memory management practices in network services.
Organizations should implement immediate mitigations including applying vendor patches if available, implementing network segmentation to limit exposure, and configuring firewall rules to restrict FTP service access to trusted networks only. The remediation strategy should include comprehensive input validation mechanisms that enforce strict limits on command length and implement proper error handling to prevent memory corruption. Additionally, system administrators should consider implementing intrusion detection systems to monitor for suspicious USER command patterns and establish regular security assessments to identify similar vulnerabilities in other network services. This vulnerability serves as a reminder of the critical need for secure coding practices and the importance of adhering to established security frameworks such as those outlined in the MITRE ATT&CK framework, particularly in the context of command and control operations where such vulnerabilities can be leveraged for initial access and privilege escalation.