Description
Jupyter Server is the backend for Jupyter web applications. Prior to 2.20, 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. This vulnerability is fixed in 2.20.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
jupyter-server jupyter_server
< 2.20affected
References
- https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmp ↗
- https://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bd ↗
- https://access.redhat.com/security/cve/CVE-2026-44727 ↗
- https://bugzilla.redhat.com/show_bug.cgi?id=2491516 ↗
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44727.json ↗
- https://access.redhat.com/errata/RHSA-2026:43038 ↗
- https://access.redhat.com/errata/RHSA-2026:60520 ↗