CVE-2005-1856 in Backup Manager
Summary
by MITRE
The CD-burning feature in backup-manager 0.5.8 and earlier uses a fixed filename in a world-writable directory for logging, which allows local users to overwrite files via a symlink attack.
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Analysis
by VulDB Data Team • 06/08/2019
The vulnerability identified as CVE-2005-1856 resides within the backup-manager software version 0.5.8 and earlier, specifically within its CD-burning feature implementation. This flaw represents a classic path traversal and privilege escalation vulnerability that exploits improper file handling practices in a system with elevated privileges. The software creates log files using a fixed filename within a directory that is world-writable, meaning any local user can write to this location. This design flaw creates a significant security risk because it allows malicious users to manipulate the logging process through symbolic link attacks.
The technical implementation of this vulnerability stems from the software's failure to properly validate or sanitize file paths during log creation operations. When backup-manager executes its CD-burning functionality, it generates log files with predictable names in directories that lack proper access controls. The fixed filename approach eliminates any randomness or user-specific identifiers that might otherwise prevent predictable file overwrite scenarios. This issue directly relates to CWE-367, which addresses the dangerous use of a predictable temporary file or directory, and CWE-276, which covers improper file permissions. The vulnerability operates under the principle that when a program runs with elevated privileges and creates files in world-writable directories without proper security controls, it becomes susceptible to symlink-based attacks.
From an operational perspective, this vulnerability enables local users to perform unauthorized file overwrites or modifications that could have severe consequences for system integrity and security. An attacker could create a symbolic link with the fixed filename in the world-writable directory, causing the backup-manager process to write log data to a location of their choosing instead of the intended log file. This capability allows for potential privilege escalation attacks where malicious users could overwrite critical system files, configuration files, or even executable programs. The impact extends beyond simple file corruption since the attacker could potentially overwrite binaries that are executed with elevated privileges, leading to arbitrary code execution. The attack vector aligns with ATT&CK technique T1059.007 for execution through scripts and T1548.001 for privilege escalation through abuse of file permissions.
The mitigation strategies for this vulnerability must address both the immediate implementation flaw and broader security practices. The most direct solution involves modifying backup-manager to either use random or unique filenames for log creation, implement proper file access controls in the logging directory, or execute the logging operations in a secure temporary directory with restricted permissions. System administrators should also ensure that world-writable directories are minimized and properly audited, as these represent common attack vectors for similar vulnerabilities. Additionally, implementing proper privilege separation and using secure file creation techniques such as the open-atomic or O_CREAT|O_EXCL flags would prevent the symlink attack scenario from succeeding. Organizations should conduct regular security assessments of backup and system management tools to identify similar path traversal vulnerabilities that could be exploited in similar contexts, particularly in systems where administrative tools run with elevated privileges and create temporary files in shared directories.