CVE-2026-40110Network attack vector

Cross-origin API access via prefix-matched Origin

Published May 5, 2026 · Updated May 5, 2026

CORS origin validation bypass in Jupyter Server 2.17.0 and earlier allows remote attackers to issue cross-origin API requests. Origin checks pass allow_origin_pat and the request Origin to re.match, which accepts a trusted-domain prefix without consuming the full value. Exploitation requires a prefix-matching configuration, attacker control of a matching-prefix domain, and active user interaction; it exposes server data and permits limited state changes.

CVSS severity5.9
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CORS origin validation bypass in Jupyter Server 2.17.0 and earlier allows remote attackers to issue cross-origin API requests. Origin checks pass allow_origin_pat and the request Origin to re.match, which accepts a trusted-domain prefix without consuming the full value. Exploitation requires a prefix-matching configuration, attacker control of a matching-prefix domain, and active user interaction; it exposes server data and permits limited state changes.

The record

CVE
CVE-2026-40110
Published
May 5, 2026
Updated
May 5, 2026
Vendor
Project Jupyter
Product
Jupyter Server
Classifications
CWE-777, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 5, 2026CVE publishedPublication date reported by the CVE source.
  2. May 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=<= 2.17.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Project Jupyter · Jupyter Serverversion=<= 2.17.0

Published CVSS scores

7.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N
5.9GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N
7.1Red Hat Security DataCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-777Regular Expression without Anchors
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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