Improper Restriction of Rendered UI Layers or Frames Affecting jupyter-server package, versions [,2.20.0)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applications- Snyk IDSNYK-PYTHON-JUPYTERSERVER-17391532
- published21 Jun 2026
- disclosed18 Jun 2026
- creditpikaball, Yo Iida, HunSec
Introduced: 18 Jun 2026
CVE-2026-44727 (opens in a new tab)How to fix?
Upgrade jupyter-server to version 2.20.0 or higher.
Overview
Affected versions of this package are vulnerable to Improper Restriction of Rendered UI Layers or Frames via the NbconvertFileHandler and NbconvertPostHandler classes when rendering user-authored notebook HTML without a proper sandbox directive in the Content-Security-Policy. An attacker can execute arbitrary scripts in the context of the Jupyter origin, exfiltrate authentication tokens, gain access to API endpoints, and potentially achieve remote code execution by crafting a notebook with malicious HTML payloads and convincing an authenticated user to visit a specific URL.
Workaround
This vulnerability can be mitigated by adding a custom content security policy in the jupyter_server_config.py file as described in the advisory.