CVE-2008-4501 in Serv-U
Summary
by MITRE
Directory traversal vulnerability in the FTP server in Serv-U 7.0.0.1 through 7.3, including 7.2.0.1, allows remote authenticated users to overwrite or create arbitrary files via a ..\ (dot dot backslash) in the RNTO command.
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Analysis
by VulDB Data Team • 11/06/2024
The vulnerability identified as CVE-2008-4501 represents a critical directory traversal flaw within the FTP server component of Serv-U versions 7.0.0.1 through 7.3, including the specific 7.2.0.1 release. This security weakness stems from inadequate input validation mechanisms within the RNTO command processing functionality, which is used for renaming files within the FTP server environment. The flaw enables authenticated remote attackers to manipulate file paths through the exploitation of ..\ sequences, effectively bypassing normal file system access controls and directory restrictions that should normally prevent such operations.
The technical implementation of this vulnerability occurs when the FTP server processes the RNTO command without properly sanitizing or validating the target file path provided by the client. When an attacker submits a path containing ..\ sequences, the server fails to adequately resolve or sanitize these path traversal components, allowing the malicious path to be interpreted as a legitimate file operation. This misconfiguration creates a condition where the server's file system operations can be manipulated to target files outside of the intended directory structure, potentially enabling attackers to overwrite critical system files or create malicious files in privileged locations.
The operational impact of this vulnerability extends beyond simple file manipulation, as it provides attackers with the capability to potentially compromise the entire FTP server infrastructure. An authenticated attacker who can successfully exploit this vulnerability could gain the ability to overwrite system configuration files, inject malicious code into critical server components, or create backdoor files that maintain persistent access to the compromised system. The vulnerability's classification under CWE-22, which specifically addresses "Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')", underscores the fundamental nature of this security flaw and its potential for widespread exploitation.
The attack vector for this vulnerability requires that an attacker first obtain valid authentication credentials to access the FTP server, which limits the scope of potential exploitation compared to unauthenticated vulnerabilities. However, once authenticated, the attacker can leverage this weakness to perform arbitrary file operations with the privileges of the FTP service account. This scenario aligns with ATT&CK technique T1078.002, which covers "Valid Accounts: Standard Accounts" and highlights how legitimate credentials can be abused to perform malicious activities within systems. The vulnerability essentially transforms legitimate FTP access into a privilege escalation vector that can be used to compromise the underlying operating system.
Mitigation strategies for CVE-2008-4501 should prioritize immediate patching of affected Serv-U versions to the latest available releases that contain proper input validation and path sanitization mechanisms. Organizations should implement strict file path validation within their FTP server configurations, ensuring that all file operations are properly sandboxed and that path traversal sequences are rejected or properly resolved. Network segmentation and access controls should be implemented to limit FTP server exposure, while monitoring systems should be configured to detect suspicious file operations, particularly those involving path traversal sequences. Additionally, regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other network services that may be susceptible to comparable directory traversal attacks.