CVE-2005-2479 in Quick N Easy FTP Server
Summary
by MITRE
Quick n Easy FTP Server 3.0 allows remote attackers to cause a denial of service (application crash or CPU consumption) via a long USER command.
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Analysis
by VulDB Data Team • 07/26/2017
The vulnerability identified as CVE-2005-2479 affects Quick n Easy FTP Server version 3.0, representing a classic denial of service flaw that exploits improper input validation in the authentication handling mechanism. This vulnerability resides within the server's USER command processing functionality, where the application fails to adequately sanitize or limit the length of user-provided input data. The flaw manifests when remote attackers submit excessively long USER commands, which triggers unpredictable behavior in the server application. Such attacks can result in either application crashes that terminate the FTP service or CPU consumption attacks that exhaust system resources, effectively rendering the service unavailable to legitimate users. The vulnerability demonstrates a fundamental weakness in input validation practices that has been documented under CWE-20, which specifically addresses "Improper Input Validation" in software security design. This particular implementation flaw allows attackers to leverage the FTP protocol's authentication sequence to disrupt service availability, making it a significant concern for network administrators managing file transfer services.
The technical exploitation of this vulnerability occurs at the protocol level where the FTP server processes the USER command without implementing proper bounds checking or input length limitations. When an attacker sends a USER command containing an excessive number of characters, the server's internal buffer handling mechanisms become overwhelmed, leading to either a stack overflow condition or memory corruption that causes the application to terminate unexpectedly. The attack vector is particularly dangerous because it requires minimal privileges and can be executed remotely without authentication, making it an attractive target for malicious actors seeking to disrupt network services. From an operational perspective, this vulnerability directly impacts the availability aspect of the CIA security triad by enabling attackers to perform denial of service attacks against the FTP server. The impact extends beyond simple service interruption as the CPU consumption aspect of the vulnerability can lead to sustained resource exhaustion that may affect other services running on the same system. This particular attack pattern aligns with ATT&CK technique T1499.004, which describes "Toggle File System Mount" and similar resource exhaustion methods that can be leveraged to disrupt service availability.
The mitigation strategies for CVE-2005-2479 should focus on implementing robust input validation mechanisms within the FTP server application. System administrators should immediately apply vendor patches or updates that address the input length validation issue in the USER command processing. Additionally, implementing network-level controls such as rate limiting and connection throttling can help reduce the impact of such attacks by limiting the number of malformed requests that can be processed within a given time period. The implementation of proper buffer management and input sanitization practices should be enforced throughout the application code to prevent similar vulnerabilities from manifesting in other protocol handling components. Organizations should also consider deploying intrusion detection systems that can identify and alert on anomalous USER command patterns that exceed normal operational parameters. From a security architecture standpoint, this vulnerability highlights the importance of defense in depth strategies that include both application-level protections and network-level monitoring to detect and prevent exploitation attempts. The remediation process should include thorough code review of all input handling mechanisms to identify similar patterns that may be susceptible to the same class of attack, ensuring comprehensive protection against related vulnerabilities.