CVE-2005-1632 in Cheetah
Summary
by MITRE
Cheetah 0.9.15 and 0.9.16 searches the /tmp directory for modules before using the paths in the PYTHONPATH variable, which allows local users to execute arbitrary code via a malicious module in /tmp/.
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Analysis
by VulDB Data Team • 07/05/2021
The vulnerability described in CVE-2005-1632 represents a critical security flaw in the Cheetah template engine version 0.9.15 and 0.9.16. This issue stems from a problematic module loading mechanism that creates an insecure path resolution behavior. The vulnerability specifically affects systems where the Cheetah template engine is used to process templates, particularly in environments where local users might have write access to the /tmp directory. The core problem lies in the order of path resolution where the system first searches the /tmp directory before checking the PYTHONPATH variable, creating an exploitable condition for privilege escalation.
This vulnerability directly maps to CWE-427 Uncontrolled Search Path Element, which describes how applications fail to properly control the search paths used to locate libraries or modules. The flaw allows local attackers to place malicious Python modules in the /tmp directory, which the Cheetah engine will then load and execute with the privileges of the user running the application. This behavior creates a significant attack surface where any local user with write permissions to /tmp can potentially execute arbitrary code, effectively bypassing normal security boundaries. The vulnerability operates under the principle of insecure module loading where the application does not properly validate or sanitize the module search paths, leading to code execution in the context of the application process.
The operational impact of CVE-2005-1632 is substantial as it provides local privilege escalation capabilities that can be exploited by attackers with minimal privileges. When a local user places a malicious Python module in /tmp, and the Cheetah engine processes templates that include this module, the malicious code executes with the privileges of the Cheetah process. This can lead to complete system compromise, data exfiltration, or further lateral movement within the network. The vulnerability is particularly dangerous in multi-user environments where users may have different privilege levels but all share the same /tmp directory. Attackers can leverage this to escalate privileges from standard user accounts to higher privilege levels, potentially gaining access to sensitive system resources or administrative functions.
Mitigation strategies for this vulnerability must address the fundamental flaw in path resolution within the Cheetah template engine. The primary recommendation involves updating to a patched version of Cheetah where the module loading mechanism properly respects the PYTHONPATH variable and does not search insecure directories like /tmp. Organizations should also implement proper file system permissions where the /tmp directory is restricted to prevent unauthorized module placement. The principle of least privilege should be enforced by ensuring that only authorized processes have write access to critical system directories. Additionally, system administrators should monitor for suspicious module files in the /tmp directory and implement security monitoring solutions that can detect unauthorized code execution attempts. From an ATT&CK perspective, this vulnerability aligns with T1068 Privilege Escalation and T1548 Abuse of Cloud Instance Metadata, as it allows local users to escalate their privileges through code injection techniques. The vulnerability also relates to T1059 Command and Scripting Interpreter where malicious Python code can be executed through the compromised template engine. Organizations should also consider implementing application whitelisting controls to prevent execution of unauthorized Python modules, and establish secure coding practices that properly validate and sanitize module paths before loading.