{"cve":"CVE-2026-44727","nvd":{"published":"2026-06-22T21:16:24.260","modified":"2026-10-25T23:10:00.167","status":"Modified","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.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","score":9.3},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N","score":5.4},"cwes":["CWE-79","CWE-1021"],"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"],"products":["jupyter:jupyter_server"],"source":"nvd","synced_at":"2026-10-25T23:44:33.281319194+00:00"},"epss":{"cve":"CVE-2026-44727","score":0.00438,"percentile":0.37805,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-fcw5-x6j4-ccmp","url":"https://osv.dev/vulnerability/GHSA-fcw5-x6j4-ccmp","summary":"Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP ","modified":"2026-09-10T03:50:49.418798509Z","packages":[{"ecosystem":"PyPI","name":"jupyter-server","purl":"pkg:pypi/jupyter-server","ranges":["<2.20.0"],"fixed":["2.20.0"]}]},{"id":"PYSEC-2026-366","url":"https://osv.dev/vulnerability/PYSEC-2026-366","summary":"Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP ","modified":"2026-07-13T16:15:26.841396760Z","packages":[{"ecosystem":"PyPI","name":"jupyter-server","purl":"pkg:pypi/jupyter-server","ranges":["<2.20.0"],"fixed":["2.20.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}