{"cve":"CVE-2026-86049","nvd":{"published":"2026-09-17T21:17:50.213","modified":"2026-09-24T21:19:05.340","status":"Awaiting Analysis","description":"Jupyter Server is the backend for Jupyter web applications. Prior to version 2.21.0, the 5xx request logging path in jupyter_server/log.py copies the Referer header into a JSON header block without applying the token scrubbing used for the request URI. A request that returns HTTP 500 while the Referer contains a token-bearing URL can therefore write that token to server logs in plaintext. An attacker who can read those logs can recover the token and use the affected user's Jupyter Server permissions. This issue is fixed in version 2.21.0.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H","score":7.1},"cwes":["CWE-532"],"references":["https://github.com/jupyter-server/jupyter_server/commit/52513529af7096e622c00911b17627b266294717","https://github.com/jupyter-server/jupyter_server/pull/1681","https://github.com/jupyter-server/jupyter_server/releases/tag/v2.21.0","https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-c3mw-737p-c7g2"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:55:23.253742848+00:00"},"epss":{"cve":"CVE-2026-86049","score":0.00416,"percentile":0.35901,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-c3mw-737p-c7g2","url":"https://osv.dev/vulnerability/GHSA-c3mw-737p-c7g2","summary":"Jupyter Server: 5xx request logging leaks token-bearing Referer header values","modified":"2026-10-01T17:55:42.193212736Z","packages":[{"ecosystem":"PyPI","name":"jupyter-server","purl":"pkg:pypi/jupyter-server","ranges":["<2.21.0"],"fixed":["2.21.0"]}]},{"id":"PYSEC-2026-4054","url":"https://osv.dev/vulnerability/PYSEC-2026-4054","summary":"Jupyter Server: 5xx request logging leaks token-bearing Referer header values","modified":"2026-10-01T17:45:05.564324201Z","packages":[{"ecosystem":"PyPI","name":"jupyter-server","purl":"pkg:pypi/jupyter-server","ranges":["<2.21.0"],"fixed":["2.21.0"]}]}],"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."]}