Special Element Injection in notebook

The primary impact of CVE-2021-32798 is remote code execution. An attacker can embed malicious code within an IPython Notebook file. When a user opens this notebook, the embedded code executes with the privileges of the user running IPython. This could allow an attacker to gain control of the system, steal sensitive data, install malware, or perform other malicious actions. The attack requires the user to actively open the malicious notebook file, but the potential impact is severe, allowing for complete system compromise. This vulnerability shares similarities with other code injection vulnerabilities where user-supplied data is executed without proper sanitization.

Users who rely on IPython Notebook for data analysis, scientific computing, or interactive development are at risk. This includes researchers, data scientists, and developers who frequently share and open notebooks from external sources. Shared hosting environments where multiple users have access to the same notebook files are particularly vulnerable.

• python / notebook: Inspect notebook files (.ipynb) for suspicious code blocks, particularly those executing shell commands or system calls.

import nbformat
from nbconvert import PythonExporter

with open('suspicious.ipynb', 'r') as f:
    nb = nbformat.read(f, as_version=4)

code = PythonExporter().from_notebook_node(nb.cells[0])
print(code)

• generic web: Monitor web server access logs for requests to download .ipynb files from untrusted sources. • generic web: Check response headers for unusual content types associated with .ipynb files.

1. 2021-08-23Disclosure

   disclosure

1. Reserviert2021-05-12
2. Veröffentlicht2021-08-23
3. Geändert2026-03-13
4. EPSS aktualisiert2026-04-02

The primary mitigation for CVE-2021-32798 is to upgrade to a patched version of IPython Notebook, specifically 5.7.11 or 6.4.1. If upgrading is not immediately feasible, exercise extreme caution when opening notebooks from untrusted sources. Consider implementing a Web Application Firewall (WAF) or proxy to inspect notebook files for malicious content before they are opened. While a direct workaround is unavailable, restricting user access to notebook files and educating users about the risks of opening untrusted files can reduce the attack surface. After upgrading, verify the fix by attempting to open a known malicious notebook (if available) and confirming that the code does not execute.