CVE-2023-28617 - Arbitrary Command Execution Vulnerability in org-babel-execute:latex of ob-latex.el in Org Mode through 9.6.1 for GNU Emacs

A security vulnerability (CVE-2023-28617) has been identified in the org-babel-execute:latex function in the ob-latex.el file of Org Mode (up to and including version 9.6.1) for GNU Emacs. The vulnerability could allow an attacker to execute arbitrary shell commands by providing a specially crafted file or directory name containing shell metacharacters. This post will provide an in-depth analysis of the vulnerability, including code snippets, original references, and exploit details.

Vulnerability Overview

The vulnerability lies in the org-babel-execute:latex function found in the org-babel-execute-src-block function call chain, which is responsible for the rendering of LaTeX code blocks. The org-babel-execute:latex function passes unescaped, user-controlled input to a shell command that is executed in an insecure manner, allowing for arbitrary command injection.

By executing an Org Mode source code block with the affected LaTeX settings, an attacker can leverage this flaw to execute arbitrary commands on the user's system.

Here is an example of code that could lead to this vulnerability

(defun org-babel-execute:latex (body params)
  (let ((out-file (org-babel-create-temp-file "latex-svg-"))
        (in-file (org-babel-temp-file "latex-"))
        (cmds (plist-get params :commands))
        (whitespace (string-to-number (cdr (assoc :preserve-indent params))))
        (input (if (equal cmds "none") body (org-latex-replace-verb body whitespace))))
    (org-babel-execute:latex-header cmds body)
    (with-temp-file in-file (insert input))
    (with-temp-buffer
      (shell-command (concat cmds
                             (format " -interaction=nonstopmode -output-directory=\"%s\" \"%s\""
                                     (file-name-directory out-file)
                                     (file-name-directory in-file))
                             (if (string-match "\\.svg$" org-latex-view-format)
                                 " && latexml --postprocessing=\"\""
                               "")
                             " " (file-name-directory in-file)))
      (buffer-string))
    out-file))

As seen above, the variable cmds, for instance, is derived directly from user input and passed to shell-command without proper input validation or escaping. This flaw enables attackers to manipulate the input, allowing command execution.

Exploit Details

The exploit would require an Org Mode file with a crafted LaTeX source code block configuration, such as the following:

#+BEGIN_SRC latex :commands "latex ; rm -rf ~/important_data"
\documentclass{article}
\begin{document}
Hello, world!
\end{document}
#+END_SRC

By executing the above code block, the attacker can run any arbitrary OS command, such as deleting sensitive data. The attacker may also compromise the target system by chaining additional commands or running a remote code execution.

Original References

1. National Vulnerability Database (NVD) Link

2. Org Mode Official Website

3. Emacs Wiki - Org Mode

Mitigation

To mitigate this vulnerability, input validation and sanitize methods should be added to the ob-latex.el file, specifically in the org-babel-execute:latex function to handle file and directory names securely.

Org Mode users should restrict executing LaTeX source code blocks whenever possible, particularly when using an untrusted or unfamiliar Org Mode file. Org Mode developers and contributors are encouraged to review the vulnerable code for possible security enhancements.

Conclusion

In conclusion, this post provides an in-depth analysis of the security vulnerability CVE-2023-28617 found in the org-babel-execute:latex function of the ob-latex.el file in Org Mode (up to and including version 9.6.1) for GNU Emacs. This vulnerability allows attackers to execute arbitrary shell commands by crafting a file name or directory containing shell metacharacters. Users are advised to be cautious when executing LaTeX source code blocks in Org Mode and adopt the recommended mitigation steps to minimize the risk of exploitation.

Timeline

Published on: 03/19/2023 03:15:00 UTC
Last modified on: 05/10/2023 01:15:00 UTC