CVE-2002-0759 in bzip2
Summary
by MITRE
bzip2 before 1.0.2 in FreeBSD 4.5 and earlier, OpenLinux 3.1 and 3.1.1, and possibly other operating systems, does not use the O_EXCL flag to create files during decompression and does not warn the user if an existing file would be overwritten, which could allow attackers to overwrite files via a bzip2 archive.
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Analysis
by VulDB Data Team • 06/24/2024
The vulnerability described in CVE-2002-0759 represents a critical file system security flaw in the bzip2 compression utility that affected multiple operating systems including FreeBSD 4.5 and earlier versions, as well as OpenLinux 3.1 and 3.1.1. This issue stems from the improper handling of file creation operations during decompression processes, where the utility fails to implement proper file system protection mechanisms that would prevent unauthorized file overwrites. The flaw specifically relates to the absence of the O_EXCL flag during file creation, which is a fundamental security practice that ensures exclusive file creation and prevents race conditions that could be exploited by malicious actors. The vulnerability is categorized under CWE-1233, which addresses the improper handling of file creation operations in compression utilities and highlights the lack of proper file system access controls during decompression activities.
The technical implementation of this vulnerability occurs when bzip2 processes compressed archives containing files that already exist in the target directory. Without the O_EXCL flag, the decompression utility performs standard file creation operations that do not check for pre-existing files with the same name, allowing attackers to craft malicious archives that overwrite critical system files, configuration files, or user data. This behavior creates a potential privilege escalation vector where an attacker could overwrite files with elevated permissions or system-critical components, depending on the context in which the decompression occurs. The flaw operates at the operating system level through the file system API calls that bzip2 uses to create and write files, making it particularly dangerous because it can be exploited through legitimate decompression operations that users might perform without suspecting malicious intent.
The operational impact of this vulnerability extends beyond simple file overwrites to encompass potential system compromise and data integrity violations. Attackers could exploit this weakness by creating specially crafted bzip2 archives containing files that overwrite system binaries, configuration files, or user data with malicious content. The vulnerability is particularly concerning in multi-user environments where users might decompress archives from untrusted sources, as it could enable attackers to modify system-critical files without proper authorization. Additionally, the lack of user warnings when overwriting existing files means that legitimate users might unknowingly overwrite important data, while attackers could leverage this behavior to silently replace files with backdoors or other malicious components. This vulnerability aligns with ATT&CK technique T1059.007 for executing malicious code through decompression utilities and represents a classic example of how seemingly benign utility operations can be weaponized for system compromise.
The recommended mitigations for CVE-2002-0759 involve immediate patching of affected systems to upgrade bzip2 to version 1.0.2 or later, which properly implements the O_EXCL flag during file creation operations. System administrators should also implement strict file access controls and permissions to minimize the impact of potential overwrites, while establishing monitoring procedures to detect unauthorized file modifications. Organizations should conduct comprehensive vulnerability assessments to identify all systems running affected versions of bzip2 and ensure proper file system integrity checks are in place. Additional defensive measures include implementing automated patch management systems, establishing secure decompression practices, and educating users about the risks of decompressing archives from untrusted sources. The vulnerability demonstrates the importance of proper file system security practices and the necessity of implementing robust file creation mechanisms that prevent race conditions and unauthorized overwrites, which are fundamental requirements for maintaining system integrity and preventing privilege escalation attacks.