CVE-2008-4394 in Portage
Summary
by MITRE
Multiple untrusted search path vulnerabilities in Portage before 2.1.4.5 include the current working directory in the Python search path, which allows local users to execute arbitrary code via a modified Python module that is loaded by the (1) ys-apps/portage, (2) net-mail/fetchmail, (3) app-editors/leo ebuilds, and other ebuilds.
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Analysis
by VulDB Data Team • 08/18/2019
The vulnerability described in CVE-2008-4394 represents a critical untrusted search path issue affecting the Portage package management system version 2.1.4.4 and earlier. This flaw stems from the improper handling of Python module loading within ebuild execution contexts, where the current working directory is inadvertently included in the Python module search path. The vulnerability falls under CWE-427 Untrusted Search Path, which is a well-documented weakness in software systems where the execution environment includes directories that should not be trusted for module loading. The specific impact occurs when Portage executes ebuild scripts that contain Python code, as these scripts inherit the current working directory in their Python path, creating a dangerous execution environment where malicious code can be loaded.
The technical implementation of this vulnerability allows local attackers to escalate privileges and execute arbitrary code by placing malicious Python modules in directories where Portage will search for required modules. The affected ebuilds mentioned in the description demonstrate the scope of the issue, as they all rely on Python-based execution contexts that are susceptible to this attack vector. The ys-apps/portage, net-mail/fetchmail, and app-editors/leo ebuilds are particularly vulnerable because they contain Python code that dynamically loads modules during execution, and the inclusion of the current working directory in the search path means that any Python file named identically to a required module will be loaded instead of the legitimate system module. This creates a classic privilege escalation scenario where local users can manipulate the module loading process to execute malicious code with the privileges of the Portage process.
The operational impact of this vulnerability extends beyond simple code execution to encompass potential system compromise and privilege escalation. When Portage executes ebuilds, it typically runs with elevated privileges to perform package installation and system modifications, making this vulnerability particularly dangerous. The attack requires local access to the system, but once exploited, it can allow attackers to modify system packages, install backdoors, or escalate privileges to root level access. The vulnerability is especially concerning in environments where Portage is used for system administration and package management, as it provides a persistent attack vector that could be exploited by malicious local users or attackers who have gained initial access to the system. This weakness directly aligns with ATT&CK technique T1068 Privilege Escalation through exploitation of software vulnerabilities, as it enables local users to leverage a flaw in system software to gain elevated privileges.
Mitigation strategies for this vulnerability should focus on immediate patching of Portage to version 2.1.4.5 or later, which contains the necessary fixes to prevent the inclusion of the current working directory in Python search paths. System administrators should also implement proper directory permissions and file integrity monitoring to detect unauthorized modifications to ebuild files and Python modules. Additionally, the principle of least privilege should be enforced by ensuring that Portage operations are performed with minimal necessary privileges, and that the Python path is explicitly set to trusted directories only. Organizations should conduct regular security audits of their package management systems and implement sandboxing techniques for ebuild execution to prevent similar vulnerabilities from being exploited in other software components. The fix implemented in Portage 2.1.4.5 specifically addresses the root cause by ensuring that the current working directory is not included in the Python module search path during ebuild execution, thereby preventing the loading of malicious modules from untrusted locations.