CVE-2005-2426 in FTPshell Server
Summary
by MITRE
FTPshell Server 3.38 allows remote authenticated users to cause a denial of service (application crash) by multiple connections and disconnections without using the QUIT command.
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Analysis
by VulDB Data Team • 06/08/2019
The vulnerability identified as CVE-2005-2426 affects FTPshell Server version 3.38 and represents a classic denial of service flaw that exploits improper connection handling mechanisms. This vulnerability specifically targets the server's response to client connection lifecycle management, where authenticated users can trigger application instability through repeated connection and disconnection sequences. The flaw demonstrates a critical weakness in the server's resource management and state tracking capabilities, as it fails to properly handle abrupt disconnections that occur without the standard QUIT command sequence. Such behavior creates a condition where the server's internal connection tracking structures become corrupted or overwhelmed, ultimately leading to application crash and service unavailability.
The technical implementation of this vulnerability stems from inadequate validation and cleanup procedures within the FTPshell Server's connection handling code. When users establish multiple connections and subsequently disconnect without properly terminating sessions via the QUIT command, the server maintains references to these incomplete connection states in its memory structures. This results in a memory leak scenario where connection handles are not properly released, and the server's internal data structures become corrupted over time. The vulnerability aligns with CWE-400, which classifies improper resource management as a significant weakness in software security. The flaw operates at the protocol level where the server fails to implement proper session cleanup routines, creating a condition where resource exhaustion occurs through legitimate authenticated access patterns.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on FTPshell Server for file transfer operations, as it can be exploited by both malicious actors and disgruntled employees with legitimate access credentials. The impact extends beyond simple service disruption, as the application crash can potentially result in data loss or corruption if connections are terminated during critical file transfer operations. The vulnerability's exploitability is relatively straightforward, requiring only authenticated access and the ability to establish multiple connection sessions, making it particularly dangerous in environments where user access controls may not be sufficiently restrictive. The flaw can be leveraged to create sustained denial of service conditions that may persist until manual server restart is performed, disrupting business continuity and potentially affecting other services dependent on the affected server.
The mitigation strategy for this vulnerability requires immediate implementation of server updates and patches provided by the vendor, as the flaw represents a fundamental design issue in the connection management architecture. Organizations should also implement connection rate limiting and monitoring mechanisms to detect anomalous connection patterns that may indicate exploitation attempts. Network-level controls can be deployed to restrict the number of concurrent connections from individual authenticated users, thereby limiting the potential impact of this vulnerability. Additionally, implementing proper session timeout mechanisms and ensuring automatic cleanup of connection resources regardless of termination method can help prevent the accumulation of invalid connection states. This vulnerability highlights the importance of robust session management practices and aligns with ATT&CK technique T1499.004, which addresses network denial of service through resource exhaustion, emphasizing the need for proper handling of connection lifecycle events in server applications.