Vulnerability Details 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 `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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.001
EPSS Ranking 3.2%
CVSS Severity
CVSS v3 Score 6.1
References
Products affected by CVE-2026-6657
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cpe:2.3:a:jupyter:jupyter_server:1.12.0
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cpe:2.3:a:jupyter:jupyter_server:1.12.1
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cpe:2.3:a:jupyter:jupyter_server:1.13.0
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cpe:2.3:a:jupyter:jupyter_server:1.13.1
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cpe:2.3:a:jupyter:jupyter_server:1.13.2
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cpe:2.3:a:jupyter:jupyter_server:1.13.3
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cpe:2.3:a:jupyter:jupyter_server:1.13.4
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cpe:2.3:a:jupyter:jupyter_server:1.13.5
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cpe:2.3:a:jupyter:jupyter_server:1.15.0
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cpe:2.3:a:jupyter:jupyter_server:1.15.1
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cpe:2.3:a:jupyter:jupyter_server:1.15.2
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cpe:2.3:a:jupyter:jupyter_server:1.15.3
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cpe:2.3:a:jupyter:jupyter_server:1.15.4
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cpe:2.3:a:jupyter:jupyter_server:1.15.5
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cpe:2.3:a:jupyter:jupyter_server:1.15.6
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cpe:2.3:a:jupyter:jupyter_server:1.16.0
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cpe:2.3:a:jupyter:jupyter_server:1.17.0
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cpe:2.3:a:jupyter:jupyter_server:1.17.1
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cpe:2.3:a:jupyter:jupyter_server:1.18.0
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cpe:2.3:a:jupyter:jupyter_server:1.18.1
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cpe:2.3:a:jupyter:jupyter_server:1.19.0
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cpe:2.3:a:jupyter:jupyter_server:1.19.1
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cpe:2.3:a:jupyter:jupyter_server:1.21.0
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cpe:2.3:a:jupyter:jupyter_server:1.23.0
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cpe:2.3:a:jupyter:jupyter_server:1.23.1
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cpe:2.3:a:jupyter:jupyter_server:1.23.2
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cpe:2.3:a:jupyter:jupyter_server:1.23.3
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cpe:2.3:a:jupyter:jupyter_server:1.23.4
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cpe:2.3:a:jupyter:jupyter_server:1.23.5
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cpe:2.3:a:jupyter:jupyter_server:1.23.6
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cpe:2.3:a:jupyter:jupyter_server:1.24.0
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cpe:2.3:a:jupyter:jupyter_server:2.0.0
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cpe:2.3:a:jupyter:jupyter_server:2.0.1
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cpe:2.3:a:jupyter:jupyter_server:2.0.2
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cpe:2.3:a:jupyter:jupyter_server:2.0.3
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cpe:2.3:a:jupyter:jupyter_server:2.0.4
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cpe:2.3:a:jupyter:jupyter_server:2.0.5
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cpe:2.3:a:jupyter:jupyter_server:2.0.6
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cpe:2.3:a:jupyter:jupyter_server:2.0.7
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cpe:2.3:a:jupyter:jupyter_server:2.1.0
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cpe:2.3:a:jupyter:jupyter_server:2.10.0
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cpe:2.3:a:jupyter:jupyter_server:2.10.1
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cpe:2.3:a:jupyter:jupyter_server:2.11.0
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cpe:2.3:a:jupyter:jupyter_server:2.11.1
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cpe:2.3:a:jupyter:jupyter_server:2.11.2
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cpe:2.3:a:jupyter:jupyter_server:2.12.0
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cpe:2.3:a:jupyter:jupyter_server:2.12.1
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cpe:2.3:a:jupyter:jupyter_server:2.12.2
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cpe:2.3:a:jupyter:jupyter_server:2.12.3
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cpe:2.3:a:jupyter:jupyter_server:2.12.4
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cpe:2.3:a:jupyter:jupyter_server:2.12.5
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cpe:2.3:a:jupyter:jupyter_server:2.13.0
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cpe:2.3:a:jupyter:jupyter_server:2.14.0
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cpe:2.3:a:jupyter:jupyter_server:2.14.1
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cpe:2.3:a:jupyter:jupyter_server:2.14.2
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cpe:2.3:a:jupyter:jupyter_server:2.15.0
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cpe:2.3:a:jupyter:jupyter_server:2.16.0
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cpe:2.3:a:jupyter:jupyter_server:2.17.0
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cpe:2.3:a:jupyter:jupyter_server:2.2.0
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cpe:2.3:a:jupyter:jupyter_server:2.2.1
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cpe:2.3:a:jupyter:jupyter_server:2.3.0
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cpe:2.3:a:jupyter:jupyter_server:2.4.0
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cpe:2.3:a:jupyter:jupyter_server:2.5.0
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cpe:2.3:a:jupyter:jupyter_server:2.6.0
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cpe:2.3:a:jupyter:jupyter_server:2.7.0
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cpe:2.3:a:jupyter:jupyter_server:2.7.1
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cpe:2.3:a:jupyter:jupyter_server:2.7.2
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cpe:2.3:a:jupyter:jupyter_server:2.7.3
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cpe:2.3:a:jupyter:jupyter_server:2.8.0
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cpe:2.3:a:jupyter:jupyter_server:2.9.0
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cpe:2.3:a:jupyter:jupyter_server:2.9.1