CVE-2011-5060 in Par-packer Module
Summary
by MITRE
The par_mktmpdir function in the PAR module before 1.003 for Perl creates temporary files in a directory with a predictable name without verifying ownership and permissions of this directory, which allows local users to overwrite files when another user extracts a PAR packed program, a different vulnerability in a different package than CVE-2011-4114.
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Analysis
by VulDB Data Team • 01/10/2018
The vulnerability identified as CVE-2011-5060 resides within the par_mktmpdir function of the PAR module for Perl, affecting versions prior to 1.003. This flaw represents a classic temporary file creation vulnerability that exploits predictable naming conventions to enable privilege escalation and file overwrite attacks. The PAR module serves as a packaging system for perl applications, allowing developers to create self-contained executables that can be distributed and executed without requiring perl to be installed on target systems. When a user extracts a PAR packed program, the system creates temporary files in directories with predictable names, creating an attack surface that can be exploited by local adversaries.
The technical implementation of this vulnerability stems from the par_mktmpdir function's failure to properly validate directory ownership and permissions before creating temporary files. This function generates temporary directories using predictable naming patterns, typically based on process identifiers or other deterministic factors that can be anticipated by attackers. When multiple users interact with PAR packed programs on the same system, the predictable directory names create opportunities for race conditions and malicious file overwrites. The vulnerability specifically manifests when one user extracts a PAR program while another user has already created a temporary directory with the same predictable name, allowing the first user to overwrite files in the second user's directory.
The operational impact of this vulnerability extends beyond simple file overwrite scenarios and represents a significant security risk in multi-user environments. Local attackers can exploit this weakness to modify or replace files that should be protected, potentially leading to privilege escalation or persistent backdoors within the system. The vulnerability operates under the broader category of insecure temporary file handling as defined by CWE-377, which specifically addresses the creation of temporary files with insecure permissions or predictable names. This weakness allows attackers to manipulate the temporary file creation process and gain unauthorized access to resources that should remain protected.
The attack vector for this vulnerability typically involves a coordinated effort between multiple users on the same system where one user creates a malicious temporary directory with predictable naming before another user extracts a PAR program. The attacker can then manipulate the environment to ensure that the PAR module creates its temporary files in the attacker-controlled directory, enabling file overwrite operations. This type of attack aligns with the tactics described in the attack pattern framework under the category of privilege escalation through insecure file handling. The vulnerability demonstrates the importance of proper directory validation and permission checking in temporary file creation processes, as outlined in various secure coding guidelines and best practices.
Mitigation strategies for CVE-2011-5060 require immediate patching of the PAR module to version 1.003 or later, which implements proper directory validation and secure temporary file creation mechanisms. System administrators should also consider implementing additional security controls such as restricting write permissions on temporary directories and monitoring for unusual file creation patterns. The vulnerability highlights the need for comprehensive security testing of packaging and distribution systems, particularly those that create temporary files during execution. Organizations should also review their deployment practices to ensure that PAR programs are not being executed in environments where multiple users share the same temporary directory space without proper isolation mechanisms. This vulnerability serves as a reminder of the critical importance of secure temporary file handling in preventing local privilege escalation attacks and maintaining system integrity across multi-user environments.