CVE-2015-1200 in pxz
Summary
by MITRE
Race condition in pxz 4.999.99 Beta 3 uses weak file permissions for the output file when compressing a file before changing the permission to match the original file, which allows local users to bypass the intended access restrictions.
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Analysis
by VulDB Data Team • 04/11/2022
The vulnerability identified as CVE-2015-1200 represents a critical race condition flaw within the pxz compression utility version 4.999.99 Beta 3. This issue stems from the software's improper handling of file permissions during the compression process, creating a window of opportunity for local attackers to exploit the system's security controls. The pxz utility, designed for parallel compression using xz format, demonstrates a fundamental weakness in its permission management protocol that directly compromises the intended security boundaries of compressed files.
The technical implementation of this vulnerability occurs during the file compression workflow where pxz creates an output file with weak, insecure permissions before subsequently modifying these permissions to match those of the original source file. This temporal gap between file creation and permission setting creates a race condition that malicious users can exploit. The flaw manifests because the utility does not properly secure the intermediate output file during the compression process, allowing unauthorized users or processes to access or modify the file contents before the intended permission changes take effect. This weakness specifically aligns with CWE-362, which categorizes race conditions as a critical class of vulnerabilities where concurrent operations can lead to inconsistent system states.
The operational impact of this vulnerability extends beyond simple unauthorized file access, as it fundamentally undermines the security model of file-based compression utilities. Local users who can execute processes on the same system can potentially read sensitive data that was intended to be protected by the original file permissions. This creates a scenario where attackers can bypass access controls that should restrict who can view or modify compressed files, particularly when these files contain confidential information. The vulnerability is particularly concerning in multi-user environments where users may not have direct access to sensitive files but could potentially exploit this weakness to gain unauthorized access to compressed data.
Security professionals should consider this vulnerability in the context of the broader ATT&CK framework, specifically under the techniques related to privilege escalation and credential access. The flaw enables local users to effectively bypass file permission controls, which represents a form of privilege escalation that operates at the file system level. Organizations using pxz in their compression workflows should implement immediate mitigations including updating to patched versions of the utility, implementing proper file permission controls, and monitoring for unauthorized file access patterns. The vulnerability also highlights the importance of secure coding practices around file handling and permission management, particularly in utilities that operate with elevated privileges or handle sensitive data. System administrators should also consider implementing additional monitoring controls to detect potential exploitation attempts and ensure that file permission changes are properly enforced throughout the compression lifecycle.