{"cve":"CVE-2026-6657","nvd":{"published":"2026-06-03T16:16:31.710","modified":"2026-07-21T19:10:00.107","status":"Analyzed","description":"A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the `allow_origin_pat` configuration is used. The issue arises from the use of `re.match()` for validating the `Origin` header, which only anchors at the start of the string. This allows attacker-controlled domains such as `trusted.example.com.evil.com` to pass validation against patterns intended to match `trusted.example.com`. The vulnerability affects multiple locations in the codebase, including CORS headers, WebSocket connections, referer validation, and login redirects, potentially enabling phishing attacks, arbitrary code execution, and unauthorized access to sensitive API responses.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","score":8.8},"cwes":["CWE-346"],"references":["https://huntr.com/bounties/18f642db-3569-43b3-b58d-ff97be4b09d7","https://huntr.com/bounties/18f642db-3569-43b3-b58d-ff97be4b09d7"],"products":["jupyter:jupyter_server"],"source":"nvd","synced_at":"2026-10-19T22:37:48.043517290+00:00"},"epss":{"cve":"CVE-2026-6657","score":0.05213,"percentile":0.92501,"date":"2026-10-31"},"kev":null,"osv":[{"id":"PYSEC-2026-3472","url":"https://osv.dev/vulnerability/PYSEC-2026-3472","summary":"jupyter-server is vulnerable to CORS origin validation bypass when the `allow_origin_pat` configuration is used","modified":"2026-07-23T15:00:15.106608390Z","packages":[{"ecosystem":"PyPI","name":"jupyter-server","purl":"pkg:pypi/jupyter-server","ranges":[">=1.12.0 <=2.17.0"],"fixed":[]}]}],"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."]}