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.

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History

Fri, 05 Jun 2026 08:45:00 +0000

Type Values Removed Values Added
First Time appeared Jupyter
Jupyter jupyter Server
Vendors & Products Jupyter
Jupyter jupyter Server

Wed, 03 Jun 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 03 Jun 2026 16:00:00 +0000

Type Values Removed Values Added
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.
Title CORS Origin Validation Bypass in jupyter-server
Weaknesses CWE-346
References
Metrics cvssV3_0

{'score': 6.1, 'vector': 'CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: @huntr_ai

Published:

Updated: 2026-06-03T17:25:20.310Z

Reserved: 2026-04-20T08:13:54.544Z

Link: CVE-2026-6657

cve-icon Vulnrichment

Updated: 2026-06-03T17:24:00.205Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-06-03T16:16:31.710

Modified: 2026-06-04T15:25:53.963

Link: CVE-2026-6657

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-06-05T08:30:24Z

Weaknesses