CVE-2008-5986 in Csound
Summary
by MITRE
Untrusted search path vulnerability in the (1) "VST plugin with Python scripting" and (2) "VST plugin for writing score generators in Python" in Csound 5.08.2, and possibly other versions, allows local users to execute arbitrary code via a Trojan horse Python file in the current working directory, related to a vulnerability in the PySys_SetArgv function (CVE-2008-5983).
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/26/2018
The vulnerability described in CVE-2008-5986 represents a critical untrusted search path weakness affecting Csound versions 5.08.2 and potentially earlier releases. This issue specifically impacts two VST plugins within the Csound audio synthesis software suite that utilize Python scripting capabilities for sound generation and score manipulation. The vulnerability stems from improper handling of Python module loading within the application's execution environment, creating a pathway for privilege escalation through malicious code injection.
The technical flaw manifests through the PySys_SetArgv function, which is responsible for setting the Python interpreter's argument vector. When Csound loads these VST plugins, it does not properly sanitize the search path used to locate Python modules, allowing attackers to place malicious Python files in the current working directory. This creates a classic race condition vulnerability where the system loads the attacker-controlled module instead of the legitimate one, as documented in CVE-2008-5983. The vulnerability operates under CWE-426, which describes the weakness of untrusted search path usage, where applications fail to properly validate or sanitize the paths used to locate executable code or libraries.
The operational impact of this vulnerability is significant for local attackers who can leverage it to execute arbitrary code with the privileges of the user running Csound. Since VST plugins are commonly used in audio production environments where users often have elevated privileges, this vulnerability could be exploited to gain unauthorized access to sensitive systems. The attack vector is particularly concerning because it requires minimal user interaction beyond placing a malicious file in a specific directory, making it an attractive target for social engineering attacks. The vulnerability affects both the VST plugin with Python scripting capabilities and the score generator plugin, indicating a fundamental flaw in how Csound handles Python module resolution across its plugin architecture.
Mitigation strategies should focus on implementing proper path validation and privilege separation within the application. System administrators should ensure that Csound installations are run with minimal necessary privileges and that the current working directory is properly secured. The most effective remediation involves updating to patched versions of Csound where the PySys_SetArgv function is properly sanitized to prevent loading of modules from untrusted paths. Additionally, implementing proper file system permissions and monitoring for unauthorized file modifications in directories where Csound plugins operate can help detect potential exploitation attempts. Organizations should also consider implementing application whitelisting policies that restrict which Python modules can be loaded by Csound applications, aligning with the principle of least privilege and reducing the attack surface. The vulnerability demonstrates the importance of secure coding practices in interpreted languages where dynamic module loading is used, particularly in environments where audio applications require extensive scripting capabilities.