Vulnerability 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 Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Jupyter | Jupyter Server | >= 1.12.0, <= 2.17.0 |
Related Weaknesses (CWE)
References
- https://huntr.com/bounties/18f642db-3569-43b3-b58d-ff97be4b09d7ExploitThird Party Advisory
- https://huntr.com/bounties/18f642db-3569-43b3-b58d-ff97be4b09d7ExploitThird Party Advisory
FAQ
What is CVE-2026-6657?
CVE-2026-6657 is a vulnerability with a CVSS score of 8.8 (HIGH). 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...
How severe is CVE-2026-6657?
CVE-2026-6657 has been rated HIGH with a CVSS base score of 8.8/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-6657?
Check the references section above for vendor advisories and patch information. Affected products include: Jupyter Jupyter Server.