5.4mediumMedium
CVE-2026-44727
Jupyter Jupyter Server
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.
Exploitation status
- A vendor advisory or patch reference has been published.
What the metrics mean
- It is reachable over a network, without needing local access.
- For an attacker who can reach it, no special conditions are needed to exploit it.
- To exploit it, an ordinary user account is needed.
- Beyond that, someone has to be persuaded to take an action first.
Scoring
- CVSS
- 5.4 (v3.1)
- Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N- CVSS v4
- 9.3
- Weakness
- CWE-79
- Assigned by
- security-advisories@github.com
Dates
- Published
- 2026-06-22
- Last modified
- 2026-08-28
- Sources
- NVD
Affected products
- Jupyter Jupyter Server- 2.20.0
As listed in the NVD configuration data. Not a statement about your estate.
References
- https://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bd
- https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmp
- https://access.redhat.com/errata/RHSA-2026:43038
- https://access.redhat.com/errata/RHSA-2026:60520
- 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