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CVE-2026-40110 — Vulnerability in jupyter-server — CVE Details

HIGH

Jupyter Server has a CORS Origin Validation Bypass via `re.match()` in `allow_origin_pat`

Published May 5, 2026Updated September 10, 2026Source: osv

Summary

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

Advisory Timeline

  • First published May 5, 2026 (160 days ago).
  • Last revised September 10, 2026 — 127 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

pip
Update jupyter-server to 2.18.0 or later
pip install "jupyter-server>=2.18.0"

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (1)

Affects 1 ecosystem: pypi (1).

PackageEcosystemAffectedFixed In
jupyter-server
pypi
0.0.0, 0.0.1, 0.0.2, 0.0.3 (+151 more)2.18.0

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 9.2 score means for each attack dimension.

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
P
Scope
—
Confidentiality
—
Integrity
—
Availability
—

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:L/SC:L/SI:L/SA:L

References

Frequently Asked Questions

What is CVE-2026-40110?
Jupyter Server has a CORS Origin Validation Bypass via `re.match()` in `allow_origin_pat` This vulnerability has been assigned a severity rating of HIGH (CVSS score: 9.2/10).
How do I check if my project is affected by CVE-2026-40110?
CVE-2026-40110 affects jupyter-server. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-40110 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score
9.2

Exploitation is straightforward and causes maximum impact. Patch immediately.

Also Known As

GHSA-24qx-w28j-9m6p
PYSEC-2026-2187

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