CVE-2003-0771 in Apache::Gallery
Summary
by MITRE
Gallery.pm in Apache::Gallery (aka A::G) uses predictable temporary filenames when running Inline::C, which allows local users to execute arbitrary code by creating and modifying the files before Apache::Gallery does.
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Analysis
by VulDB Data Team • 05/04/2019
The vulnerability described in CVE-2003-0771 affects Apache::Gallery, a Perl module used for serving web-based image galleries within Apache web servers. This module leverages the Inline::C Perl module to execute C code dynamically, which introduces a critical security flaw in how temporary files are handled during the compilation process. The issue stems from the predictable naming scheme used for temporary files generated during Inline::C execution, creating a race condition that local attackers can exploit to gain arbitrary code execution privileges.
The technical flaw resides in the improper handling of temporary file creation within the Apache::Gallery module's integration with Inline::C. When Apache::Gallery processes image gallery requests, it dynamically generates C code and compiles it using Inline::C. The module creates temporary files with predictable names and locations, typically within standard temporary directories such as /tmp or /var/tmp. This predictable naming allows local users to anticipate and manipulate the temporary files before the legitimate Apache::Gallery process attempts to use them, creating a window of opportunity for malicious file replacement.
The operational impact of this vulnerability is severe as it enables local privilege escalation attacks that can lead to complete system compromise. An attacker with local access to the system can create symbolic links or replace temporary files with malicious content before Apache::Gallery executes the compiled C code. Since Apache::Gallery typically runs with elevated privileges, particularly when processing user requests, successful exploitation can result in arbitrary code execution with the privileges of the Apache user, potentially allowing attackers to gain full control over the web server and underlying system. This vulnerability directly maps to CWE-362, which describes a race condition that occurs when a program has a window of time between checking for a condition and acting on it, and also aligns with ATT&CK technique T1068, which covers exploitation of remote services for privilege escalation.
The vulnerability exploitation requires an attacker to have local access to the system and knowledge of the predictable temporary file naming scheme used by Apache::Gallery. Attackers can create malicious files with the same predictable names in the temporary directories, effectively hijacking the compilation process. The race condition occurs during the execution of Inline::C, where the module creates temporary files, and the attacker must ensure their malicious files are in place before Apache::Gallery attempts to read or execute them. This timing aspect makes the attack feasible but requires careful coordination with the target process execution.
Mitigation strategies for this vulnerability include updating to newer versions of Apache::Gallery that address the temporary file handling issue and implement proper randomization of temporary file names. System administrators should ensure that all web server modules and dependencies are kept up to date with security patches, particularly in environments where local users may exist. Additional protective measures involve restricting write permissions to temporary directories, implementing proper file access controls, and using privilege separation techniques to limit the impact of potential exploitation. Organizations should also consider implementing monitoring for suspicious file creation patterns in temporary directories and regularly audit system configurations to prevent similar vulnerabilities in other modules that may use similar dynamic code generation techniques. The fix typically involves modifying the temporary file creation logic to use random or unique identifiers that cannot be predicted by attackers, thereby eliminating the race condition window that enables this particular exploit.