Jupyter Server has a CORS Origin Validation Bypass via `re.match()` in `allow_origin_pat`
GHSA-24qx-w28j-9m6p · CVE-2026-40110 · PYSEC-2026-2187
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Description
Jupyter Server uses re.match() to validate the Origin header against the allow_origin_pat configuration.
Since re.match() only anchors at the start of the string, an attacker who controls a domain like http://trusted.example.com.evil.com/ passes validation against a pattern intended to match only trusted.example.com.
Impact
<=2.17.0
Patches
057869a327c46730afede3eab0ca2d2e3e74acea, 49b34392feaa97735b3b777e3baf8f22f2a14ed8
Workarounds
Wrap your allow_origin_pat value with ^ and $
References
https://github.com/jupyter-server/jupyter_server/pull/603
https://docs.python.org/3/library/re.html#re.fullmatch
https://docs.python.org/3/library/re.html#re.match
References
- WEB https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-24qx-w28j-9m6p
- ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-40110
- WEB https://github.com/jupyter-server/jupyter_server/pull/603
- WEB https://github.com/jupyter-server/jupyter_server/commit/057869a327c46730afede3eab0ca2d2e3e74acea
- WEB https://github.com/jupyter-server/jupyter_server/commit/49b34392feaa97735b3b777e3baf8f22f2a14ed8
- WEB https://access.redhat.com/errata/RHSA-2026:43038
- WEB https://access.redhat.com/security/cve/CVE-2026-40110
- WEB https://bugzilla.redhat.com/show_bug.cgi?id=2466912
- PACKAGE https://github.com/jupyter-server/jupyter_server
- WEB https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2026-2187.yaml
- WEB https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40110.json
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