CVE-2012-5905 in KnFTPd
Summary
by MITRE
Buffer overflow in KnFTPd 1.0.0 allows remote authenticated users to cause a denial of service (crash) via a long string in a FEAT command.
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Analysis
by VulDB Data Team • 07/05/2025
The vulnerability identified as CVE-2012-5905 represents a critical buffer overflow flaw within KnFTPd version 1.0.0, a file transfer protocol server implementation. This security weakness specifically manifests when the server processes a malformed FEAT command, which is part of the standard ftp protocol for feature negotiation. The vulnerability stems from inadequate input validation and bounds checking mechanisms within the server's command processing logic, creating a condition where maliciously crafted input can exceed the allocated buffer space and overwrite adjacent memory regions.
The technical exploitation of this vulnerability occurs through a remote authenticated attack vector, meaning that an attacker must first establish a legitimate FTP session with the target server before executing the malicious payload. When the FEAT command receives an excessively long string input, the server's internal buffer handling mechanism fails to properly validate the input length against predefined limits, resulting in a classic stack-based buffer overflow condition. This overflow corrupts the program's execution flow and ultimately leads to an application crash, rendering the FTP service unavailable to legitimate users.
From an operational impact perspective, this vulnerability creates a significant denial of service condition that can be exploited by malicious actors to disrupt critical file transfer operations within organizations relying on KnFTPd for data exchange. The vulnerability's remote nature means that attackers can target the service from outside the network perimeter without requiring physical access or complex attack infrastructure. The crash condition effectively terminates the FTP service process, forcing administrators to manually restart the service and potentially disrupting business operations that depend on file transfer capabilities. This type of vulnerability directly impacts availability as defined by the CIA security triad and can be classified under CWE-121 as a stack-based buffer overflow.
The attack pattern associated with this vulnerability aligns with the MITRE ATT&CK framework's execution and privilege escalation tactics, as attackers can leverage the service disruption to gain further access opportunities or to establish persistent access through subsequent exploitation attempts. Organizations using KnFTPd 1.0.0 are particularly vulnerable since this version has known security weaknesses that have been addressed in subsequent releases. The vulnerability demonstrates poor secure coding practices related to input validation and memory management, which are fundamental requirements in secure software development methodologies. Network administrators should consider implementing network segmentation and monitoring for unusual FTP command patterns as part of their defensive strategies. The recommended mitigation includes immediate patching of the KnFTPd server to the latest version that contains proper input validation and buffer overflow protection mechanisms. Additionally, implementing proper access controls and monitoring for anomalous FTP command sequences can help detect potential exploitation attempts before they succeed in causing service disruption.