Vulnerability · CVE-2026-6657
A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the configuration is used.
Published Jun 3, 2026 · corrected/updated Jul 21, 2026 · jupyter jupyter server · evidence confidence medium
A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the configuration is used. The issue arises from the use of for validating the header, which only anchors at the start of the string. This allows attacker-controlled domains such as to pass validation against patterns intended to match . 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.
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-6657 is a high public vulnerability record for jupyter jupyter server. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether jupyter jupyter server is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: jupyter/jupyter server. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 8.8. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-346. Sources contributing to this record: nvd. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Jun 3, 2026 · NIST NVD
Detected
A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the configuration is used. The issue arises from the use of for validating the header, which only anchors at the start of the string. This allows attacker-controlled domains such as to pass validation against patterns intended to match . The vulnerability affects multiple locat
Jul 21, 2026 · NIST NVD
Updated
A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the configuration is used. The issue arises from the use of for validating the header, which only anchors at the start of the string. This allows attacker-controlled domains such as to pass validation against patterns intended to match . The vulnerability affects multiple locat
Affected
- cpe jupyter/jupyter serverversion unspecified
Sources
- NIST NVDVulnerability recordCVE-2026-6657
A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the configuration is used. The issue arises from the use of for validating the header, which only anchors at the star
nvd.nist.gov