CVE-2004-0148 in wu-ftpd
Summary
by MITRE
wu-ftpd 2.6.2 and earlier, with the restricted-gid option enabled, allows local users to bypass access restrictions by changing the permissions to prevent access to their home directory, which causes wu-ftpd to use the root directory instead.
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Analysis
by VulDB Data Team • 07/13/2025
The vulnerability identified as CVE-2004-0148 represents a critical access control flaw within the wu-ftpd file transfer protocol implementation that affected versions 2.6.2 and earlier. This issue specifically manifests when the restricted-gid option is enabled, creating a scenario where local users can manipulate file permissions to circumvent intended security restrictions. The flaw stems from the daemon's improper handling of directory access controls, where it fails to properly validate user permissions before determining the appropriate directory context for file operations.
The technical mechanism behind this vulnerability involves the interaction between the restricted-gid feature and the file permission model within the wu-ftpd daemon. When users modify permissions on their home directories to prevent access, the daemon incorrectly interprets this as a signal to default to the root directory structure instead of maintaining proper isolation. This misinterpretation occurs because the software does not adequately verify the integrity of directory access controls before executing file operations, allowing unauthorized access to system resources that should remain restricted to specific user groups or individuals.
From an operational perspective, this vulnerability creates a significant escalation path for local attackers who can leverage the permission manipulation technique to gain access to files and directories that would normally be restricted. The impact extends beyond simple unauthorized file access, as attackers can potentially discover system configuration files, user data, and other sensitive information that resides in directories accessible through the root directory path. This vulnerability directly violates the principle of least privilege and undermines the fundamental security model that wu-ftpd attempts to enforce through its restricted-gid functionality.
The vulnerability aligns with CWE-276, which describes improper file permissions, and demonstrates how inadequate access control validation can lead to privilege escalation. From an ATT&CK framework perspective, this issue maps to privilege escalation techniques where local users can manipulate system resources to gain broader access rights. The vulnerability also represents a failure in input validation and access control enforcement, creating a path for attackers to bypass intended security boundaries within the file transfer service.
Mitigation strategies for CVE-2004-0148 include immediate patching of wu-ftpd to versions that address the permission handling flaw, disabling the restricted-gid option if it is not essential for operations, and implementing proper file system access controls that prevent users from modifying directory permissions in ways that could circumvent access restrictions. Additionally, system administrators should conduct thorough audits of file permissions and access controls, implement monitoring for unusual permission changes, and consider migrating to more modern and secure FTP implementations that properly enforce access control boundaries. The vulnerability underscores the importance of proper privilege separation and access control validation in network services, particularly those that handle user authentication and file access operations.