External risk intelligence

Emacs Org Mode Allows Unsafe Function Expansion in Links

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2024-39331

Emacs is a text editor and integrated development environment typically used as a local desktop application. The vulnerability exists within Org Mode link expansion, a feature used for document processing. It is not a network-exposed service, gateway, or internet-facing application, and exposure requires a user to open a maliciously crafted file locally.

Code Injection

Gnu Emacs

before 29.4

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability has been identified in Emacs's Org Mode, which could allow for the execution of unsafe functions when processing specific link types. While the primary concern is confirming relevance and exposure due to the application's typical local use, the potential for uncontrolled function expansion requires attention.

Unsafe link expansion in Org Mode.
Could allow unintended command execution.
Confirm relevance and local exposure.

Attack Path

How an attacker could exploit the issue

An attacker could trick a user into opening a specially crafted Org Mode file within Emacs. This file could contain a malicious link designed to execute arbitrary commands on the user's system by bypassing security checks in how Org Mode handles link abbreviations. If successful, this could allow an attacker to gain control of the affected system.

No special access required.
Malicious Org Mode link in a file.
Arbitrary command execution.

Live Threat

Current exploitation, exposure, and threat context

When Org Mode in Emacs processes specific link types, it may incorrectly expand abbreviations that execute unsafe commands. This could lead to the execution of arbitrary commands by an attacker if a user opens a specially crafted file.

Arbitrary command execution could affect Emacs users.
Opening a malicious Org Mode file could trigger it.
System compromise is a realistic consequence.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in Emacs' Org Mode affects users who process specially crafted links. System owners and platform teams should first identify instances of Emacs and Org Mode, determine if any processed documents are exposed to untrusted sources, and then coordinate remediation.

Identify all Emacs/Org Mode instances.
Verify exposure to untrusted data.
Plan remediation or mitigation.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

Free EASM Trial See How Signal Works

Frequently asked questions

What is GNU Emacs and Org Mode?

GNU Emacs is a powerful, extensible text editor and integrated development environment often used for programming and documentation. Org Mode is a built-in feature set within Emacs designed for managing notes, maintaining lists, and authoring documents. It uses special syntax to create links and format content, which is where this vulnerability specifically resides.

How does CVE-2024-39331 function as a vulnerability?

This issue is classified as CWE-94, or Improper Control of Generation of Code. In plain English, the software fails to properly sanitize input, allowing it to interpret text as executable code. In this specific case, the Org Mode link abbreviation system is tricked into running arbitrary commands, such as shell operations, instead of just opening a standard reference.

Do I need to be online for this to trigger?

No, an internet connection is not required to trigger this bug. The vulnerability requires a user to open a malicious, specially crafted Org Mode file locally within their editor. Simply having Emacs installed or viewing non-malicious documents will not trigger the flaw; it depends entirely on the content of the file being processed.

Is my system at risk according to Halo Surface Signal?

Halo Surface Signal assesses the risk as very unlikely because Emacs is typically used as a local desktop application rather than an internet-facing service. Since the software does not automatically expose a network port to the web, the primary threat vector is limited to a user manually opening an untrusted file on their own machine.

When should I update Emacs to fix this?

You should prioritize updating to Emacs version 29.4 or later as soon as your operational workflow allows. Because this vulnerability involves the execution of arbitrary commands, it is important to treat any instances of Emacs that regularly open documents from untrusted or external sources with urgency to prevent potential system compromise.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.