CVE-2008-3294 in Vim
Summary
by MITRE
src/configure.in in Vim 5.0 through 7.1, when used for a build with Python support, does not ensure that the Makefile-conf temporary file has the intended ownership and permissions, which allows local users to execute arbitrary code by modifying this file during a time window, or by creating it ahead of time with permissions that prevent its modification by configure.
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Analysis
by VulDB Data Team • 08/19/2019
The vulnerability described in CVE-2008-3294 represents a critical security flaw in the Vim text editor version 5.0 through 7.1 that specifically affects builds configured with Python support. This issue stems from improper handling of temporary files during the build process, creating a window of opportunity for privilege escalation attacks. The vulnerability is particularly concerning because it allows local users to execute arbitrary code with elevated privileges, potentially compromising the entire system.
The technical flaw exists within the src/configure.in script which manages the build configuration process for Vim. When configuring a build with Python support, the script creates a temporary file named Makefile-conf that should be properly secured with appropriate ownership and permissions. However, the configuration script fails to enforce these security measures, leaving the temporary file vulnerable to manipulation. This weakness creates a race condition scenario where an attacker can modify the temporary file during the build process or pre-create it with malicious permissions that prevent the legitimate configure script from modifying it.
The operational impact of this vulnerability is significant as it enables local privilege escalation attacks through a well-known attack pattern that aligns with the attack technique described in the MITRE ATT&CK framework under T1068 for local privilege escalation. An attacker with access to the system can exploit this vulnerability to execute arbitrary code with the privileges of the build process, which typically runs with elevated permissions. This could result in complete system compromise, especially when combined with other attack vectors or when the build process is executed by users with administrative privileges.
The vulnerability manifests through two primary exploitation methods that align with common privilege escalation techniques documented in industry standards. The first method involves timing attacks during the build process where an attacker modifies the temporary file while the configure script is running, potentially injecting malicious code or altering build parameters. The second method allows attackers to pre-create the temporary file with specific permissions that prevent the legitimate configuration process from modifying it, effectively hijacking the build process. Both approaches leverage the principle of least privilege violation and represent classic examples of temporary file handling vulnerabilities.
Effective mitigation strategies for this vulnerability include ensuring that the Vim build process properly sets file ownership and permissions for temporary files, implementing proper file locking mechanisms, and conducting thorough security reviews of build scripts. System administrators should avoid running build processes with elevated privileges when possible and ensure that all temporary files are created with restrictive permissions. The vulnerability also highlights the importance of following secure coding practices and adhering to standards such as those outlined in the CWE database under category 377 for insecure temporary file handling. Regular updates to Vim and other software packages are essential to prevent exploitation of known vulnerabilities, and security audits should specifically examine build scripts for similar temporary file handling issues that could lead to privilege escalation attacks.