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9.4
Jupyter Server may let malicious notebooks steal tokens
published 1 month ago
Summary
The Jupyter Server component that converts notebooks to HTML can display hidden HTML code from a notebook without proper protection. An attacker who places such code in a notebook can trick a logged‑in user into revealing their authentication token and possibly run commands on the server. Updating to the latest version of the python-jupyter-server package removes the unsafe setting.
What to do
- Update openeuler python-jupyter-server to version 2.13.0-3.oe2403sp4.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| openEuler:24.03-LTS-SP4 | openeuler | python-jupyter-server |
< 2.13.0-3.oe2403sp4 Fix: upgrade to 2.13.0-3.oe2403sp4
|
Original advisory text
python-jupyter-server security update
The backend for Jupyter web applications
Security Fix(es):
The nbconvert HTTP handlers in jupyter_server render user-authored notebook HTML under the Jupyter origin without a sandbox directive in their `Content-Security-Policy`. Combined with `nbconvert.HTMLExporter`'s default non-sanitizing behavior, a notebook carrying an HTML payload in a display_data output triggers stored XSS with cookie access, full /api/* authority, and kernel RCE. An authenticated victim who navigates to `/nbconvert/html/<path>` containing attacker-authored output can have their token exfiltrated to another domain because it is executed in the Jupyter origin.(CVE-2026-44727)
Security Fix(es):
The nbconvert HTTP handlers in jupyter_server render user-authored notebook HTML under the Jupyter origin without a sandbox directive in their `Content-Security-Policy`. Combined with `nbconvert.HTMLExporter`'s default non-sanitizing behavior, a notebook carrying an HTML payload in a display_data output triggers stored XSS with cookie access, full /api/* authority, and kernel RCE. An authenticated victim who navigates to `/nbconvert/html/<path>` containing attacker-authored output can have their token exfiltrated to another domain because it is executed in the Jupyter origin.(CVE-2026-44727)
References
- https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-44727 Vendor Advisory
Internet-facing
14 days
Internal
At next upgrade
- Not known to be exploited
- Needs hands-on effort to exploit (estimated)
- Gives an attacker full control (estimated)
Timeline
Published20 Sep 2026
Updated20 Sep 2026
First seen20 Sep 2026
Sources
OESA-2026-3956 · OSV
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