CVE-2003-1232 in Emacs
Summary
by MITRE
Emacs 21.2.1 does not prompt or warn the user before executing Lisp code in the local variables section of a text file, which allows user-assisted attackers to execute arbitrary commands, as demonstrated using the mode-name variable.
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Analysis
by VulDB Data Team • 10/22/2024
The vulnerability identified as CVE-2003-1232 represents a critical security flaw in Emacs version 21.2.1 that fundamentally undermines user safety through improper handling of local variables within text files. This issue stems from the editor's failure to implement adequate security measures when processing local variables that contain executable Lisp code, creating a dangerous execution environment where malicious code can be silently invoked without user awareness or consent.
The technical flaw manifests in Emacs's local variables processing mechanism where the software automatically evaluates Lisp expressions contained within the local variables section of text files without any user prompting or warning. When an attacker constructs a text file containing malicious Lisp code within the local variables area, specifically utilizing variables like mode-name, the editor executes this code upon file opening. This behavior directly violates fundamental security principles of user consent and explicit authorization for code execution, creating an environment where arbitrary commands can be executed with the privileges of the user running Emacs.
The operational impact of this vulnerability extends beyond simple code execution to encompass a broad range of potential attacks that can compromise system integrity and user security. Attackers can leverage this flaw to execute arbitrary commands, potentially leading to privilege escalation, data theft, or system compromise. The vulnerability is particularly dangerous because it operates silently without user notification, making it difficult to detect and prevent. The use of mode-name as a demonstration variable shows that any local variable containing executable Lisp code can serve as an attack vector, expanding the scope of potential exploitation.
This vulnerability aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and relates to the broader category of code injection attacks where untrusted data is executed as code. The flaw also connects to ATT&CK technique T1059.006, "Command and Scripting Interpreter: Python", through the execution of arbitrary commands, though in this case the interpreter is Lisp rather than Python. The vulnerability represents a classic example of insufficient input validation and code execution control, where the system blindly trusts content from local files without proper sanitization or user verification.
Mitigation strategies for CVE-2003-1232 require immediate action including updating to a patched version of Emacs where the local variables section handling has been properly secured. Users should implement strict file access controls and avoid opening untrusted text files with Emacs, particularly those from unknown sources. System administrators should consider implementing additional security measures such as sandboxing Emacs processes or using file integrity monitoring to detect suspicious local variable modifications. The most effective long-term solution involves ensuring that all versions of Emacs properly validate and sanitize local variables before execution, implementing user prompts for potentially dangerous code execution, and establishing secure defaults that prevent automatic evaluation of untrusted Lisp expressions. Organizations should also conduct security awareness training to educate users about the risks of opening untrusted files and the importance of verifying file sources before processing them with text editors that support code execution features.