CVE-1999-1394 in FreeBSD
Summary
by MITRE
BSD 4.4 based operating systems, when running at security level 1, allow the root user to clear the immutable and append-only flags for files by unmounting the file system and using a file system editor such as fsdb to directly modify the file through a device.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 06/29/2024
This vulnerability exists in berkeley software distribution versions 4.4 and earlier operating systems when configured with security level 1. The flaw stems from inadequate privilege separation and file system protection mechanisms that allow a root user to bypass mandatory access controls through a specific exploitation technique. The vulnerability is categorized under cwe-264 permissions, privileges, and access control issues, specifically involving improper handling of file system flags and security level configurations. When the system operates at security level 1, it permits certain administrative operations while still maintaining core security restrictions that should prevent modification of critical file attributes.
The technical execution involves mounting a file system, unmounting it to gain direct device access, and then utilizing file system editors like fsdb to directly manipulate file system structures. This approach circumvents normal file system interfaces and access control mechanisms that would typically prevent modification of immutable and append-only flags. The attack vector leverages the fact that at security level 1, while the system maintains some protective measures, it does not fully enforce the restrictions necessary to prevent direct device manipulation by privileged users. This technique represents a privilege escalation path that allows root to bypass file system integrity controls, which is particularly concerning because these flags are designed to protect critical system files from modification.
The operational impact of this vulnerability is significant as it undermines fundamental file system security principles and allows for complete bypass of file integrity protections. An attacker with root access can modify critical system files and directories by removing protective flags, potentially leading to system compromise, data corruption, or persistent backdoor installation. The vulnerability demonstrates a critical flaw in the security model implementation where the security level configuration does not properly enforce the necessary restrictions for file system integrity. This weakness can be exploited to maintain persistence on a system by modifying system binaries, configuration files, or log files without detection, as the normal auditing and protection mechanisms are bypassed.
Mitigation strategies should focus on implementing proper file system security configurations and avoiding security level 1 configurations where direct device access is permitted. System administrators should ensure that file systems are properly mounted with appropriate security parameters and that direct device access is restricted even for root users. The recommended approach involves implementing stricter access controls through cwe-264 compliant privilege management and ensuring that file system editors like fsdb are properly restricted. Additionally, organizations should consider implementing file integrity monitoring solutions and regular security audits to detect unauthorized modifications. This vulnerability highlights the importance of following the principle of least privilege and proper security level enforcement as outlined in various security frameworks and standards that address access control and file system integrity protection.