CVE-2014-1831 in Passenger
Summary
by MITRE
Phusion Passenger before 4.0.37 allows local users to write to certain files and directories via a symlink attack on (1) control_process.pid or a (2) generation-* file.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 04/16/2022
Phusion Passenger is a popular web application server that facilitates the deployment of ruby applications on web servers such as apache and nginx. The vulnerability identified as CVE-2014-1831 affects versions prior to 4.0.37 and represents a significant security flaw that could enable local attackers to manipulate critical system files through a carefully crafted symlink attack. This vulnerability resides in the way Passenger handles certain temporary and control files during its operation, creating opportunities for privilege escalation and unauthorized file modifications.
The technical flaw manifests in the insecure handling of file paths during the creation and management of control files such as control_process.pid and generation-* files. These files are essential for Passenger's process management and application deployment operations. When Passenger creates these files, it does not properly validate or sanitize the file paths, allowing attackers to establish symbolic links that point to sensitive system locations before the legitimate files are created. This race condition vulnerability occurs because the application first checks for file existence and then creates files without proper atomic operations or secure temporary file handling mechanisms. The flaw aligns with CWE-367, which addresses time-of-check to time-of-use vulnerabilities where an attacker can manipulate resources between the time of a check and the time of use.
The operational impact of this vulnerability is substantial for systems running affected versions of Phusion Passenger. Local attackers who can write to the directories where Passenger operates can potentially overwrite critical system files, modify application configurations, or escalate privileges to gain unauthorized access to system resources. The attack vector specifically targets the control_process.pid file and generation-* files, which are used for process management and application version control respectively. An attacker could exploit this vulnerability to inject malicious code into the application deployment process or to manipulate the application's behavior by overwriting legitimate control files with malicious counterparts. This vulnerability directly relates to ATT&CK technique T1059 which involves executing malicious code through command and script interpreters, and T1548.001 which addresses privilege escalation through hijacking system processes.
The vulnerability stems from improper file path handling and lacks proper file system access controls during the creation of temporary files. When Passenger creates these control files, it does not implement secure file creation practices such as using atomic file operations or verifying file ownership before writing. The implementation fails to consider the potential for attackers to establish symlinks in the same directories where Passenger creates its control files, creating a window where malicious files can be written to unintended locations. Organizations using Phusion Passenger versions prior to 4.0.37 are particularly at risk since this vulnerability allows for persistent manipulation of the application deployment environment without requiring external network access or elevated privileges beyond local system access. The fix for this vulnerability required implementing proper file path validation and secure file creation procedures that prevent the exploitation of time-of-check to time-of-use race conditions.
Organizations should immediately upgrade to Phusion Passenger version 4.0.37 or later to remediate this vulnerability. System administrators should also implement additional security measures such as restricting write permissions to directories where Passenger operates, monitoring for unauthorized file modifications, and implementing proper file system access controls. The vulnerability highlights the importance of secure file handling practices in application servers and the critical need for atomic operations when creating system files. Regular security audits should include verification of file system permissions and the implementation of proper access controls to prevent similar vulnerabilities from being exploited in other applications. This vulnerability serves as a reminder that even seemingly benign file operations can create significant security risks when proper safeguards are not implemented in the application code.