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CVE-2026-40110

jupyter-server CORS origin validation bypass via unanchored regex in allow_origin_pat

Published: May 5, 2026Updated: May 11, 2026 Sources: CVE List NVDCWE-777
NVD MITRE
7.3CVSSHIGH
EPSS Score
0.4%
Top 72.6%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

Description

Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, the Origin header validation uses Python's re.match() to check incoming origins against the allow_origin_pat configuration value. Because re.match() only anchors at the start of the string and does not require a full match, a pattern intended to match only a trusted domain (e.g., trusted.example.com) will also match any origin that begins with that domain followed by additional characters (e.g., trusted.example.com.evil.com). An attacker who controls such a domain can bypass the CORS origin restriction and make cross-origin requests to the Jupyter Server API from an untrusted site. This issue has been fixed in version 2.18.0.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:RS:UC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None
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Weaknesses

CWE-777

Affected Products

jupyter serverjupyter
Mixed
AI / ML / notebook-mlops
jupyter_serverjupyter-server
On-prem
AI / ML / notebook-mlops
jupyteross-projectAI / MLaka notebook, jupyter server, jupyterlab
jupyter-serveross-projectUSAI / MLaka jupyter_server, jupyter-scheduler

Exploitability

Official Patch Available

References

https://github.com/jupyter-server/jupyter_server/commit/057869a327c46730afede3eab0ca2d2e3e74acea
github.com
https://github.com/jupyter-server/jupyter_server/commit/49b34392feaa97735b3b777e3baf8f22f2a14ed8
github.com
https://github.com/jupyter-server/jupyter_server/pull/603
github.com
and 1 more references View all →

Timeline

Published
May 5, 2026
Last Updated
May 11, 2026

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