CVE-2001-1335 in CesarFTP
Summary
by MITRE
Directory traversal vulnerability in CesarFTP 0.98b and earlier allows remote authenticated users (such as anonymous) to read arbitrary files via a GET with a filename that contains a ...%5c (modified dot dot).
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Analysis
by VulDB Data Team • 02/28/2025
The vulnerability identified as CVE-2001-1335 represents a critical directory traversal flaw within CesarFTP version 0.98b and earlier implementations. This security weakness specifically affects the file retrieval functionality of the FTP server, where the application fails to properly validate user-supplied filenames during GET operations. The vulnerability is particularly dangerous because it can be exploited by remotely authenticated users including anonymous users who have access to the FTP service. The flaw manifests when a malicious user constructs a filename parameter containing the sequence ...%5c which represents a modified dot dot traversal pattern. This particular encoding bypasses standard input sanitization mechanisms that typically prevent directory traversal attacks by filtering out conventional path traversal sequences such as "../" or "..\".
The technical exploitation of this vulnerability occurs at the application layer where the FTP server processes user requests without adequate validation of the filename parameter. When the GET command is issued with a crafted filename containing the ...%5c sequence, the FTP server interprets this as a request to traverse directories and access files outside the intended directory structure. This misinterpretation results in the server returning arbitrary files from the underlying file system, potentially exposing sensitive data including configuration files, user credentials, system logs, and other confidential information. The vulnerability stems from insufficient input validation and improper path resolution mechanisms within the FTP server implementation, creating a direct path to unauthorized file access that violates fundamental security principles of least privilege and proper access control.
The operational impact of CVE-2001-1335 extends beyond simple unauthorized file access to encompass significant data exposure risks that can compromise entire system security postures. Remote authenticated attackers can leverage this vulnerability to extract sensitive information from the target system, potentially leading to credential theft, system compromise, and further lateral movement within the network. The vulnerability affects the confidentiality aspect of the CIA triad by enabling unauthorized data disclosure, while also potentially undermining integrity and availability through the potential for data manipulation or system disruption. Organizations running affected CesarFTP versions face substantial risk of data breaches, regulatory compliance violations, and potential legal consequences due to exposure of sensitive information. The vulnerability is particularly concerning because it requires minimal privileges for exploitation, as even anonymous users with basic FTP access can leverage this flaw to access system files.
Security mitigations for CVE-2001-1335 should focus on immediate patching of the affected CesarFTP installations to versions that properly implement input validation and path resolution controls. Organizations should implement network segmentation to limit FTP access to trusted networks and consider disabling unnecessary FTP services where possible. The remediation process should include thorough input validation of all filename parameters, proper sanitization of user-supplied data, and implementation of secure coding practices that prevent directory traversal vulnerabilities. This vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, and maps to ATT&CK technique T1078 for valid accounts and T1566 for malicious file execution through compromised FTP services. Additional defensive measures include implementing web application firewalls, monitoring FTP access logs for suspicious directory traversal patterns, and conducting regular security assessments to identify similar vulnerabilities in other network services. The incident highlights the importance of proper input validation and secure coding practices in preventing fundamental security flaws that can lead to complete system compromise.