CVE-2024-39331 in Emacs
Summary
by MITRE • 06/24/2024
In Emacs before 29.4, org-link-expand-abbrev in lisp/ol.el expands a %(...) link abbrev even when it specifies an unsafe function, such as shell-command-to-string. This affects Org Mode before 9.7.5.
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Analysis
by VulDB Data Team • 03/22/2025
The vulnerability described in CVE-2024-39331 represents a critical security flaw within the Emacs text editor's Org Mode implementation that enables arbitrary code execution through crafted link abbreviations. This issue affects versions prior to Emacs 29.4 and Org Mode 9.7.5, where the org-link-expand-abbrev function in lisp/ol.el fails to properly validate or sanitize function references within link abbreviations. The flaw specifically occurs when processing %(...) syntax in link abbreviations that reference potentially dangerous functions such as shell-command-to-string, which can execute system commands and provide attackers with unauthorized access to underlying operating systems.
The technical nature of this vulnerability stems from insufficient input validation and privilege escalation within the Emacs Org Mode parsing mechanism. When users encounter specially crafted Org documents containing malicious link abbreviations, the system automatically processes these constructs without proper sanitization checks. The %(...) syntax in Org Mode allows for dynamic content generation through function calls, but the vulnerability arises because the system does not distinguish between safe and unsafe function invocations. This creates an environment where attackers can embed commands that execute with the privileges of the Emacs process, potentially leading to complete system compromise.
From an operational impact perspective, this vulnerability poses significant risks to users who process untrusted Org documents, particularly in collaborative environments or when downloading content from external sources. The flaw can be exploited through social engineering attacks where users unknowingly open maliciously crafted Org files that contain hidden link abbreviations. The attack vector is particularly dangerous because it operates within the legitimate parsing mechanisms of Emacs, making it difficult to detect through traditional security monitoring approaches. Security researchers have identified this issue as a potential pathway for privilege escalation and remote code execution, aligning with common attack patterns documented in the MITRE ATT&CK framework under techniques such as command and control and privilege escalation.
The vulnerability's classification aligns with CWE-78 and CWE-94 within the Common Weakness Enumeration system, representing issues in command injection and code injection respectively. These weaknesses occur when user-supplied data is directly incorporated into command or code execution contexts without proper validation or sanitization. Organizations and individuals using Emacs with Org Mode should immediately upgrade to versions 29.4 or later, where the vulnerability has been patched through enhanced input validation mechanisms. The fix implements stricter checks on function references within link abbreviations, preventing the execution of potentially dangerous functions while maintaining legitimate functionality for safe operations. System administrators should also consider implementing additional security controls such as file access restrictions, sandboxing mechanisms, and regular security audits to minimize potential exposure while awaiting full patch deployment across all systems.