CVE-2006-4974 in WS FTP Server
Summary
by MITRE
Buffer overflow in Ipswitch WS_FTP Limited Edition (LE) 5.08 allows remote FTP servers to execute arbitrary code via a long response to a PASV command.
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Analysis
by VulDB Data Team • 07/22/2024
The vulnerability identified as CVE-2006-4974 represents a critical buffer overflow flaw within Ipswitch WS_FTP Limited Edition version 5.08 that specifically targets the handling of FTP protocol responses. This issue manifests when a remote FTP server sends an excessively long response to a PASV command, which is a standard command used in FTP connections to establish data transfer modes. The flaw exists in the client-side implementation where the software fails to properly validate the length of incoming response data, creating an exploitable condition that can be leveraged by malicious actors to gain unauthorized control over affected systems.
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 specific exploitation occurs during the PASV command processing phase, where the WS_FTP client allocates a fixed-size buffer to store the server response without adequate length validation. When a malicious FTP server sends a response exceeding the allocated buffer capacity, the excess data overflows into adjacent memory regions, potentially corrupting program execution flow and allowing arbitrary code execution. This type of vulnerability demonstrates the classic stack-based buffer overflow pattern where the return address or other critical program variables get overwritten with attacker-controlled data.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with full system compromise capabilities. An attacker positioned to intercept or control an FTP server connection can leverage this flaw to execute malicious code with the privileges of the WS_FTP client process, which typically runs with the permissions of the logged-in user. This presents significant risks for environments where users connect to untrusted FTP servers, as the vulnerability can be exploited through man-in-the-middle attacks or by compromising legitimate FTP servers that are configured to send malicious responses. The exploitability is enhanced by the fact that the PASV command is commonly used in standard FTP operations, making the attack surface relatively broad.
Mitigation strategies for this vulnerability should include immediate patching of the WS_FTP client software to the latest available version that addresses the buffer overflow condition. Organizations should implement network segmentation and firewall rules to restrict FTP traffic to trusted servers only, particularly when using older versions of the software. Additionally, network monitoring should be enhanced to detect unusual FTP responses that might indicate exploitation attempts. The ATT&CK framework categorizes this type of vulnerability under T1059.007 for command and scripting interpreter, as the successful exploitation would likely involve executing commands through the compromised client process. Security teams should also consider implementing application whitelisting policies to prevent unauthorized FTP client installations and ensure that users are not running vulnerable versions of the software in their environments.