{"id":"CVE-2026-44727","summary":"Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP","details":"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.","aliases":["GHSA-fcw5-x6j4-ccmp","PYSEC-2026-366"],"modified":"2026-07-09T03:51:39.630540797Z","published":"2026-06-22T19:56:56.776Z","related":["CGA-743g-gqmr-xrp8","openSUSE-SU-2026:11159-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44727.json","cwe_ids":["CWE-1021","CWE-79"],"cna_assigner":"GitHub_M"},"references":[{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44727.json"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-44727"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44727.json"},{"type":"ADVISORY","url":"https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44727"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2491516"},{"type":"FIX","url":"https://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bd"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/jupyter-server/jupyter_server","events":[{"introduced":"0"},{"fixed":"05a78ad879e69ef87e91b2714a8ebeb5ff9628a7"},{"fixed":"6cbee8d65e71abac851c4492fea987ad080580bd"}],"database_specific":{"source":["CPE_RANGE","REFERENCES"],"cpe":"cpe:2.3:a:jupyter:jupyter_server:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"0"},{"fixed":"2.20.0"}]}}],"versions":["v2.19.0","v2.18.2","v2.18.1","v2.18.0","v2.17.0","v2.16.0","v2.15.0","v2.14.2","v2.14.1","v2.14.0","v2.13.0","v2.12.5","v2.12.4","v2.12.3","v2.12.2","v2.12.1","v2.12.0","v2.11.2","v2.11.1","v2.11.0","v2.10.1","v2.10.0","v2.9.1","v2.9.0","v2.8.0","v2.7.3","v2.7.2","v2.7.1","v2.7.0","v2.6.0","v2.5.0","v2.4.0","v2.3.0","v2.2.1","v2.2.0","v2.1.0","v2.0.7","v2.0.6","v2.0.5","v2.0.4","v2.0.3","v2.0.2","v2.0.1","v2.0.0","v2.0.0rc8","v2.0.0rc7","v2.0.0rc6","v2.0.0rc5","v2.0.0rc4","v2.0.0rc3","v2.0.0rc2","v2.0.0rc1","v2.0.0rc0","v2.0.0b1","v2.0.0b0","v2.0.0a2","v2.0.0a1","v2.0.0a0","v1.16.0","v1.15.6","v1.15.5","v1.15.4","v1.15.3","v1.15.2","v1.15.1","v1.15.0","v1.13.5","v1.13.4","v1.13.3","v1.13.2","v1.13.1","v1.13.0","v1.12.1","v1.12.0","v1.11.2","v1.11.1","v1.11.0","v1.10.2","v1.10.1","v1.10.0","v1.9.0","v1.8.0","v1.7.0","v1.7.0a2","v1.7.0a1","v1.7.0a0","v1.6.4","v1.6.3","v1.6.2","1.6.1","1.6.0","1.5.1","1.5.0","1.4.1","1.4.0","1.3.0","1.2.3","1.2.2","1.2.1","1.2.0","1.1.4","1.1.3","1.1.2","1.1.1","1.1.0","1.0.5","1.0.4","1.0.3","1.0.2","1.0.1","1.0.0","1.0.0rc16","1.0.0rc15","1.0.0rc14","1.0.0rc13","1.0.0rc12","1.0.0rc11","1.0.0rc10","1.0.0rc9","1.0.0rc8","1.0.0rc7","1.0.0rc6","1.0.0rc5","1.0.0rc4","1.0.0rc3","1.0.0rc2","1.0.0rc1","0.3.0","0.2.0","0.1.1","0.1.0","0.0.5","0.0.4","0.0.3","0.0.2","0.0.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-44727.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"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"}]}