CVE-2008-5147 in docvert
Summary
by MITRE
test-pipe-to-pyodconverter.org.sh in docvert 2.4 allows local users to overwrite arbitrary files via a symlink attack on the /tmp/outer.odt temporary file.
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Analysis
by VulDB Data Team • 10/14/2018
The vulnerability described in CVE-2008-5147 represents a classic file system race condition and symlink attack scenario that affects the docvert 2.4 document conversion tool. This issue arises from improper temporary file handling during the conversion process, specifically within the test-pipe-to-pyodconverter.org.sh script that is part of the docvert suite. The vulnerability enables local attackers to manipulate the system by creating malicious symbolic links that can cause the system to write sensitive data to arbitrary locations on the file system.
The technical flaw manifests when the docvert application creates temporary files in the /tmp directory without proper security measures to prevent symlink attacks. During the document conversion process, the application generates a temporary file named /tmp/outer.odt and subsequently processes it through the test-pipe-to-pyodconverter.org.sh script. The vulnerability occurs because the script does not validate the integrity of the temporary file path or ensure that the file is created with proper permissions and ownership. Attackers can exploit this by creating a symbolic link with the same name as the temporary file, causing the application to write data to a location controlled by the attacker rather than the intended temporary location.
This vulnerability falls under the category of CWE-377 - Insecure Temporary File Creation and CWE-378 - Creation of Temporary File With Insecure Permissions, both of which are well-documented in the Common Weakness Enumeration database. The operational impact of this vulnerability is significant as it allows local privilege escalation and potential arbitrary file overwrite capabilities. An attacker with local access can leverage this weakness to overwrite critical system files, configuration files, or even executable binaries, potentially leading to complete system compromise. The attack requires only local user access and does not necessitate network connectivity or complex exploitation techniques.
The vulnerability aligns with several tactics described in the MITRE ATT&CK framework, particularly those related to privilege escalation and persistence. Attackers can use this weakness as part of a broader exploitation strategy to establish persistent access to systems. The attack vector is relatively straightforward and can be executed by any local user, making it particularly dangerous in multi-user environments where privilege separation is not properly enforced. The exploitation process typically involves creating a symbolic link in the /tmp directory before the vulnerable script executes, effectively hijacking the temporary file creation process.
Mitigation strategies for this vulnerability involve implementing proper temporary file handling practices that ensure files are created with appropriate permissions and ownership. The recommended approach includes using secure temporary file creation functions that prevent symlink attacks, implementing proper file path validation, and ensuring that temporary files are created with restrictive permissions. Additionally, system administrators should consider running the docvert application with reduced privileges and implementing proper file system permissions to limit the impact of such vulnerabilities. The vulnerability also highlights the importance of proper input validation and secure coding practices in preventing race condition exploits that can lead to arbitrary file overwrites. Organizations should conduct regular security assessments of their document processing systems and ensure that all temporary file operations follow secure coding guidelines to prevent similar vulnerabilities from being exploited in production environments.