CVE-2021-32798 is a critical-severity (CVSS 9.6) Cross-site Scripting (XSS) vulnerability in notebook. 1 public exploit reference exists, so weaponization risk is real. A fix is available for notebook — see the affected versions and patch details below.
Special Element Injection in notebook
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-32798 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
notebook🐍notebookReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Untrusted notebook can execute code on load. This is a remote code execution, but requires user action to open a notebook.
Patches
5.7.11, 6.4.1
References
OWASP Page on Injection Prevention
For more information
If you have any questions or comments about this advisory, or vulnerabilities to report, please email our security list [email protected].
Credit: Guillaume Jeanne from Google
Example:
A notebook with the following content in a cell and it would display an alert when opened for the first time in Notebook (in an untrusted state):
{ "cell_type": "code", "execution_count": 0, "metadata": {}, "outputs": [ { "data": { "text/html": [ "<select><iframe></select><img src=x: onerror=alert('xss')>\n"], "text/plain": [] }, "metadata": {}, "output_type": "display_data" } ], "source": [ "" ] }
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | notebook | all versions | 5.7.11pip install --upgrade 'notebook==5.7.11' |
| 🐍PyPI | notebook | ≥ 6.0.0&&< 6.4.1 | 6.4.1pip install --upgrade 'notebook==6.4.1' |
Affected Products
notebookjupyterResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for notebook, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update notebook to 5.7.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32798 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2021-32798 in your dependencies?
Find it across PyPI, including transitive dependencies.