CVE-2001-0767 in GuildFTPd
Summary
by MITRE
Directory traversal vulnerability in GuildFTPd 0.9.7 allows attackers to list or read arbitrary files and directories via a .. in (1) LS or (2) GET.
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Analysis
by VulDB Data Team • 05/11/2019
The vulnerability identified as CVE-2001-0767 represents a critical directory traversal flaw in GuildFTPd version 0.9.7 that fundamentally compromises the security boundaries of the file transfer protocol server. This weakness stems from inadequate input validation within the server's handling of file listing and retrieval commands, specifically affecting the LS (list) and GET (retrieve) operations. The vulnerability allows remote attackers to exploit the server's failure to properly sanitize directory path components, enabling them to navigate beyond the intended file system boundaries and access arbitrary files or directories that should remain protected.
The technical implementation of this vulnerability exploits the fundamental nature of Unix-style file systems where the double dot sequence ".." serves as a navigation command to move up one directory level. When GuildFTPd processes commands containing these traversal sequences without proper validation, the server fails to restrict access to parent directories, allowing attackers to construct malicious file paths that bypass normal access controls. This flaw operates at the application layer of the network stack, specifically within the FTP protocol implementation where file system operations are translated into server-side actions. The vulnerability directly maps to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks.
The operational impact of this vulnerability extends far beyond simple information disclosure, as it provides attackers with the capability to enumerate entire directory structures and retrieve sensitive files that may contain configuration data, user credentials, application source code, or other confidential information. An attacker could potentially access system files, application binaries, database files, or user home directories, depending on the server's configuration and the privileges under which GuildFTPd operates. The vulnerability affects both the listing functionality that reveals directory contents and the retrieval functionality that allows downloading of files, making it particularly dangerous as it enables both reconnaissance and data exfiltration phases of an attack. This type of vulnerability aligns with ATT&CK technique T1083, which covers directory and file discovery, and T1566, covering credential harvesting through various attack vectors.
Mitigation strategies for CVE-2001-0767 should focus on immediate patching of the GuildFTPd server to a version that properly validates and sanitizes directory path inputs. Organizations should implement strict input validation mechanisms that reject or normalize directory traversal sequences before processing any file system operations. Network segmentation and firewall rules can help limit exposure by restricting access to FTP services to trusted networks only. Additionally, implementing proper access controls and privilege separation ensures that even if an attacker exploits this vulnerability, they cannot escalate their access beyond the limitations of the compromised FTP service. Regular security audits of file transfer protocols and comprehensive vulnerability assessments should be conducted to identify similar weaknesses in other FTP implementations or related network services. The vulnerability demonstrates the critical importance of input validation in network services and the potential consequences of inadequate security controls in legacy software implementations.