CVE-2003-0041 in Linux
Summary
by MITRE
Kerberos FTP client allows remote FTP sites to execute arbitrary code via a pipe (|) character in a filename that is retrieved by the client.
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Analysis
by VulDB Data Team • 08/26/2025
The vulnerability described in CVE-2003-0041 represents a critical security flaw in Kerberos FTP client implementations that enables remote code execution through improper input validation. This issue specifically affects the handling of filenames during FTP operations where the Kerberos client processes file listings from remote servers. The vulnerability stems from the client's failure to properly sanitize or escape special characters in filenames, creating a dangerous condition where malicious actors can inject command sequences that get executed by the client's underlying shell or command processing mechanisms.
The technical flaw manifests when the Kerberos FTP client encounters a filename containing the pipe character | during file retrieval operations. This character is commonly used in Unix-like systems and shell environments as a command separator, allowing the output of one command to be passed as input to another. When the client processes such filenames without proper sanitization, it inadvertently passes these strings to shell execution functions, enabling attackers to inject arbitrary commands that execute with the privileges of the FTP client process. This vulnerability operates at the intersection of command injection and improper input validation issues, aligning with CWE-78 which specifically addresses improper neutralization of special elements used in OS commands.
The operational impact of this vulnerability is severe as it allows remote attackers to execute arbitrary code on systems running the vulnerable Kerberos FTP client without requiring authentication or prior access to the system. An attacker can craft malicious filenames on a remote FTP server that, when retrieved by the client, trigger code execution. This creates a significant risk for organizations that use Kerberos authentication for FTP access, as the vulnerability can be exploited through legitimate file transfer operations. The attack vector is particularly dangerous because it requires no special privileges on the target system and can be triggered through normal file listing operations, making it difficult to detect and prevent.
This vulnerability directly relates to several MITRE ATT&CK techniques including T1059.004 for command and script interpreter, T1068 for exploit for privilege escalation, and T1203 for exploitation for execution. Organizations should implement immediate mitigations including updating to patched versions of Kerberos implementations, implementing strict input validation for filenames, and configuring network segmentation to limit access to vulnerable FTP clients. Additionally, administrators should consider disabling unnecessary FTP functionality, implementing proper network monitoring to detect suspicious command execution patterns, and applying the principle of least privilege to reduce the impact of potential exploitation. The vulnerability highlights the critical importance of proper input sanitization in security-critical applications and demonstrates how seemingly benign features can become attack vectors when proper security controls are not implemented.