CVE-2002-0761 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 systems, uses the permissions of symbolic links instead of the actual files when creating an archive, which could cause the files to be extracted with less restrictive permissions than intended.
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Analysis
by VulDB Data Team • 06/24/2024
The vulnerability described in CVE-2002-0761 represents a critical security flaw in the bzip2 compression utility that affected multiple Unix-like operating systems including FreeBSD 4.5 and earlier versions, as well as OpenLinux 3.1 and 3.1.1. This issue stems from a fundamental mismanagement of file permissions during the archive creation process, creating a significant vector for privilege escalation and unauthorized access to sensitive system resources. The flaw specifically manifests when bzip2 processes symbolic links during archive creation, where it incorrectly inherits permissions from the symbolic link itself rather than from the target file that the link points to, potentially leading to security implications that can be exploited by malicious actors.
The technical nature of this vulnerability lies in the improper handling of symbolic link permissions within the bzip2 utility's file processing logic. When bzip2 encounters a symbolic link during archive creation, it should evaluate the permissions of the actual target file to ensure proper archive metadata is maintained. However, the flawed implementation causes the utility to use the permissions of the symbolic link itself, which may have different or more permissive access controls than the underlying file. This discrepancy can result in compressed archives containing files that, when extracted, maintain less restrictive permissions than originally intended, potentially exposing sensitive data to unauthorized users or processes with lower privilege levels.
The operational impact of this vulnerability extends beyond simple permission mismanagement, creating potential security risks that align with CWE-276, which addresses improper file permissions. Attackers could exploit this weakness by creating symbolic links with more permissive permissions than the actual files they point to, then using bzip2 to create archives that would subsequently extract files with these less restrictive permissions. This behavior could be particularly dangerous in multi-user environments where system administrators rely on proper file permissions to maintain security boundaries. The vulnerability essentially undermines the integrity of file permission enforcement mechanisms, potentially allowing attackers to bypass intended access controls and gain unauthorized access to sensitive system resources.
From a threat modeling perspective, this vulnerability fits within the ATT&CK framework under the T1068 technique for "Exploitation for Privilege Escalation," as it provides a method for attackers to manipulate file permissions to achieve higher privileges. The flaw also relates to T1078 which addresses valid accounts and legitimate credentials, since it could be exploited by users who might not have direct access to sensitive files but could manipulate the archive creation process to extract files with more permissive settings. Organizations running affected versions of bzip2 should consider this vulnerability as part of their broader security posture assessment, particularly in environments where file access controls are critical for maintaining system integrity.
The recommended mitigations for this vulnerability include immediate patching of affected bzip2 versions to 1.0.2 or later, which contains the necessary fixes to properly handle symbolic link permissions. System administrators should also implement monitoring for unusual archive creation activities, particularly when symbolic links are involved, and consider implementing additional file permission checks during archive extraction processes. Organizations should conduct thorough vulnerability assessments to identify any existing archives that may have been created with compromised permissions, and implement proper access control policies that limit who can create symbolic links in sensitive directories. Additionally, regular security audits should verify that file permissions are correctly maintained throughout the system, and automated tools should be deployed to detect potential permission inconsistencies that could indicate exploitation attempts.