How severe is CVE-2026-40864?

CVE-2026-40864 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity low, and availability low.

Is CVE-2026-40864 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (5th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40864?

CVE-2026-40864 affects Jupyter Jupyterhub. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-40864?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-40864 have an EU (EUVD) identifier?

Yes. CVE-2026-40864 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-31499.

When was CVE-2026-40864 published?

CVE-2026-40864 was published on 2026-05-22 and last updated on 2026-06-17.

CVE-2026-40864

CVE-2026-40864 is a medium-severity vulnerability in Jupyter Jupyterhub with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-352.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
EPSS exploit prediction: 0% (5th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-31499
Weakness: CWE-352
Affected product: Jupyter Jupyterhub
Published: 2026-05-22
Last modified: 2026-06-17

Description

JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. In versions 4.1.0 through 5.4.4, XSRF protection (updated in 4.1.0) inappropriately treated requests with Sec-Fetch-Mode: no-cors as same-origin requests, bypassing XSRF checks. The JSON API is not affected, only HTTP form endpoints, such as /hub/spawn and /hub/accept-share, meaning attackers could trigger server spawn (but not access the server) and if the attacker is a JupyterHub user permitted to share access to their server, cause a user to accept a share and have access to the attacker's server. This issue has been fixed in version 5.4.5. If developers are unable to immediately upgrade, they can temporarily mitigate this issue by dropping requests to JupyterHub with Sec-Fetch-Mode: no-cors if they are using a reverse proxy.

Frequently asked questions

What is CVE-2026-40864?: JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. In versions 4.1.0 through 5.4.4, XSRF protection (updated in 4.1.0) inappropriately treated requests with Sec-Fetch-Mode: no-cors as same-origin requests, bypassing XSRF checks. The JSON API is not affected, only HTTP form endpoints, such as /hub/spawn and /hub/accept-share, meaning attackers could trigger server spawn (but not access the server) and if the attacker is a JupyterHub user permitted to share access to their server, cause a user to accept a share and have access to the attacker's server. This issue has been fixed in version 5.4.5. If developers are unable to immediately upgrade, they can temporarily mitigate this issue by dropping requests to JupyterHub with Sec-Fetch-Mode: no-cors if they are using a reverse proxy.
How severe is CVE-2026-40864?: CVE-2026-40864 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity low, and availability low.
Is CVE-2026-40864 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (5th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-40864?: CVE-2026-40864 affects Jupyter Jupyterhub. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-40864?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-40864 have an EU (EUVD) identifier?: Yes. CVE-2026-40864 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-31499.
When was CVE-2026-40864 published?: CVE-2026-40864 was published on 2026-05-22 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:jupyter:jupyterhub:*:*:*:*:*:*:*:*

More vulnerabilities in Jupyter Jupyterhub

CVE-2024-28233 — High (CVSS 8.1): JupyterHub is an open source multi-user server for Jupyter notebooks. By tricking a user into visiting a malicious…
CVE-2024-41942 — High (CVSS 7.2): JupyterHub is software that allows one to create a multi-user server for Jupyter notebooks. Prior to versions 4.1.6 and…
CVE-2026-33709 — Medium (CVSS 6.1): JupyterHub is software that allows one to create a multi-user server for Jupyter notebooks. Prior to version 5.4.4, an…
CVE-2019-10255 — Medium (CVSS 6.1): An Open Redirect vulnerability for all browsers in Jupyter Notebook before 5.7.7 and some browsers (Chrome, Firefox) in…
CVE-2020-36191 — Medium (CVSS 4.5): JupyterHub 1.1.0 allows CSRF in the admin panel via a request that lacks an _xsrf field, as demonstrated by a…
CVE-2021-41247 — Low (CVSS 3.5): JupyterHub is an open source multi-user server for Jupyter notebooks. In affected versions users who have multiple…

All CVEs affecting Jupyter Jupyterhub →

Other CWE-352 (Cross-Site Request Forgery (CSRF)) vulnerabilities

CVE-2025-32642 — Critical (CVSS 10.0): Cross-Site Request Forgery (CSRF) vulnerability in appsbd Vite Coupon vite-coupon allows Remote Code Inclusion.This…
CVE-2025-23922 — Critical (CVSS 10.0): Cross-Site Request Forgery (CSRF) vulnerability in Harsh iSpring Embedder embed-ispring allows Upload a Web Shell to a…
CVE-2017-5145 — Critical (CVSS 10.0): An issue was discovered in Carlo Gavazzi VMU-C EM prior to firmware Version A11_U05, and VMU-C PV prior to firmware…
CVE-2019-25729 — Critical (CVSS 9.8): PDF Signer 3.0 contains a server-side template injection vulnerability that allows unauthenticated attackers to execute…
CVE-2025-48340 — Critical (CVSS 9.8): Cross-Site Request Forgery (CSRF) vulnerability in Danny Vink User Profile Meta Manager user-profile-meta allows…
CVE-2025-2907 — Critical (CVSS 9.8): The Order Delivery Date WordPress plugin before 12.3.1 does not have authorization and CSRF checks when importing…

Browse all CWE-352 (Cross-Site Request Forgery (CSRF)) vulnerabilities →