CVE-2006-0950 in unalz
Summary
by MITRE
unalz 0.53 allows user-assisted attackers to overwrite arbitrary files via an ALZ archive with ".." (dot dot) sequences in a filename.
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Analysis
by VulDB Data Team • 07/21/2018
The vulnerability described in CVE-2006-0950 affects unalz version 0.53, a utility designed for extracting files from ALZ compressed archives. This flaw represents a classic path traversal vulnerability that enables malicious actors to manipulate the extraction process and overwrite arbitrary files on the target system. The vulnerability specifically arises when processing archive filenames containing ".." sequences, which are commonly used in path traversal attacks to navigate up directory levels. When the unalz utility processes such filenames, it fails to properly validate or sanitize the paths, allowing attackers to specify locations outside the intended extraction directory.
The technical implementation of this vulnerability stems from inadequate input validation within the archive extraction routine. When an ALZ archive contains filenames with ".." sequences, the extraction process does not properly resolve these paths or enforce directory boundaries, leading to a situation where files can be written to any location accessible to the user running the extraction utility. This behavior aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal. The flaw essentially allows attackers to bypass normal file system access controls by constructing malicious archive contents that exploit the lack of proper path validation during decompression operations.
The operational impact of this vulnerability extends beyond simple file overwrites, as it can potentially enable more sophisticated attack vectors including privilege escalation, system compromise, or data destruction. An attacker who can influence the contents of an ALZ archive can use this vulnerability to overwrite critical system files, configuration files, or even executables, depending on the privileges of the user running the unalz utility. This type of vulnerability is particularly dangerous in environments where users can upload or receive compressed files from untrusted sources, as it allows for arbitrary file system modifications without requiring direct system access or elevated privileges. The vulnerability also demonstrates the importance of proper input sanitization in archive processing utilities and aligns with ATT&CK technique T1059.007 for execution through command and scripting interpreter, as the compromised system may be used to execute malicious code through overwritten files.
Mitigation strategies for this vulnerability include immediate patching of the unalz utility to version 0.54 or later, which contains the necessary fixes for proper path validation. System administrators should implement strict file validation policies for archive files received from external sources, including scanning for potentially malicious path sequences before processing. The recommended approach involves implementing robust input validation that rejects or normalizes filenames containing ".." sequences, ensuring that all extracted paths remain within the intended target directory. Additionally, privilege separation should be enforced when running archive extraction utilities, limiting the potential damage from successful exploitation. Organizations should also consider implementing automated monitoring for unauthorized file modifications and establish proper file access controls to minimize the impact of potential exploitation. The vulnerability highlights the critical need for security-conscious development practices and proper validation of user-supplied data in all file processing operations, particularly those involving archive extraction and decompression functions.