CVE-2008-3949 in Linux
Summary
by MITRE
emacs/lisp/progmodes/python.el in Emacs 22.1 and 22.2 imports Python script from the current working directory during editing of a Python file, which allows local users to execute arbitrary code via a Trojan horse Python file.
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Analysis
by VulDB Data Team • 08/02/2021
The vulnerability described in CVE-2008-3949 represents a critical security flaw in the Emacs text editor version 22.1 and 22.2 that specifically affects the python.el module responsible for Python programming mode functionality. This issue stems from a design oversight in how Emacs handles Python script execution during the editing process, creating an environment where malicious actors can exploit local privilege escalation through carefully crafted Trojan horse files. The vulnerability operates by leveraging the default behavior of Emacs when processing Python files, which automatically imports Python scripts from the current working directory without proper validation or sandboxing measures.
The technical implementation of this vulnerability involves the python.el module's improper handling of Python script imports during editing operations. When a user opens a Python file for editing in Emacs, the system attempts to import Python modules from the current working directory, which is typically the same location as the file being edited. This behavior creates a race condition and privilege escalation vector where a local attacker can place a malicious Python script with the same name as a module that would normally be imported, causing Emacs to execute the attacker-controlled code instead of the legitimate module. The flaw specifically impacts the program modes functionality within Emacs, particularly the python.el component that manages Python-specific editing features and integration with Python environments.
The operational impact of this vulnerability extends beyond simple code execution, as it represents a privilege escalation vector that allows local users to gain unauthorized access to system resources and potentially execute arbitrary commands with the privileges of the user running Emacs. This creates a significant risk for developers and system administrators who rely on Emacs for their daily work, particularly in environments where multiple users share the same system or where untrusted code might be present in shared directories. The vulnerability is particularly dangerous because it requires no network connectivity or external attack vectors, making it exploitable through simple local file manipulation and leveraging the trust relationship between the text editor and the file system.
Mitigation strategies for this vulnerability involve both immediate patching and operational security measures to prevent exploitation. The most effective solution is to upgrade to a patched version of Emacs that addresses the improper import handling in the python.el module, ensuring that the editor no longer automatically imports scripts from the current working directory during Python file editing. Additionally, system administrators should implement strict file permissions and directory access controls to limit the ability of local users to place malicious files in directories where Emacs might execute code. The vulnerability aligns with CWE-22 (Improper Limiting of a Pathname to a Restricted Directory) and represents a classic example of insufficient input validation and privilege escalation through insecure file handling. From an ATT&CK perspective, this vulnerability maps to T1059 (Command and Scripting Interpreter) and T1548.001 (Abuse Elevation Control Mechanism) as it enables local privilege escalation through code execution and leverages the legitimate functionality of a text editor to bypass security controls.