| Name | CVE-2026-44727 |
| 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. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
Vulnerable and fixed packages
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|
| jupyter-server (PTS) | bullseye | 1.2.2-1 | vulnerable |
| bookworm | 1.23.3-1 | vulnerable |
| trixie | 2.15.0-1 | vulnerable |
| forky, sid | 2.20.0-3 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|
| jupyter-server | source | (unstable) | 2.20.0-1 | | | |
Notes
[trixie] - jupyter-server <no-dsa> (Minor issue)
[bookworm] - jupyter-server <postponed> (Minor issue; stored XSS in nbconvert handlers, present, revisit with next update)
[bullseye] - jupyter-server <postponed> (Minor issue; stored XSS in nbconvert handlers, present, revisit with next update)
https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmp
Fixed by: https://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bd (v2.20.0)