CVE-2006-4847 in WS FTP Server
Summary
by MITRE
Multiple buffer overflows in Ipswitch WS_FTP Server 5.05 before Hotfix 1 allow remote authenticated users to execute arbitrary code via long (1) XCRC, (2) XSHA1, or (3) XMD5 commands.
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Analysis
by VulDB Data Team • 02/21/2017
The vulnerability identified as CVE-2006-4847 represents a critical buffer overflow flaw affecting Ipswitch WS_FTP Server version 5.05 prior to Hotfix 1. This issue stems from inadequate input validation within the server's handling of specific extended cryptographic commands, creating exploitable conditions that could allow malicious actors to execute arbitrary code on the affected system. The vulnerability specifically impacts three distinct commands: XCRC, XSHA1, and XMD5, which are used for file integrity verification and cryptographic operations within the FTP protocol implementation.
The technical nature of this vulnerability aligns with CWE-121, which categorizes buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The flaw occurs when the server processes these extended commands without proper validation of input length, enabling attackers to craft malicious payloads that exceed the allocated buffer space. This allows for stack corruption and potential code execution, as the overflow can overwrite return addresses and other critical memory structures. The vulnerability requires authentication to exploit, meaning that an attacker must first establish valid credentials to the FTP server, but once authenticated, they can leverage this flaw to gain elevated privileges or execute arbitrary commands.
The operational impact of CVE-2006-4847 extends beyond simple code execution, as it provides attackers with persistent access to the compromised system. This vulnerability can be exploited through the standard FTP protocol, making it particularly dangerous in environments where FTP services are exposed to untrusted networks. The affected commands are part of the extended FTP protocol specification, which means that legitimate users might unknowingly trigger the vulnerability during normal file operations, potentially leading to extended periods of unauthorized access. The attack vector falls under the MITRE ATT&CK framework's technique T1059 for command and scripting interpreter, as successful exploitation would enable adversaries to execute commands with the privileges of the FTP service account.
Mitigation strategies for this vulnerability should focus on immediate patch application, as Ipswitch released Hotfix 1 to address these buffer overflow conditions. Organizations should also implement network segmentation to limit access to FTP services, enforce strong authentication mechanisms, and monitor for unusual FTP activity patterns that might indicate exploitation attempts. Additional defensive measures include implementing intrusion detection systems that can identify malformed extended FTP commands and configuring access controls to restrict which users can execute the vulnerable commands. The vulnerability demonstrates the importance of proper input validation and memory management in server applications, particularly those handling cryptographic operations where buffer overflows can lead to complete system compromise. Organizations should also consider implementing application-level firewalls and regularly reviewing their FTP server configurations to ensure that unnecessary extended commands are disabled.