Is CVE-2026-40864 in the CISA KEV catalog?

No. CVE-2026-40864 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-40864?

CVE-2026-40864 has a CVSS v3 base score of 5.4 (MEDIUM).

What is the EPSS score for CVE-2026-40864?

CVE-2026-40864 has an EPSS score of 0.16% (5th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-40864?

Upgrade jupyterhub to 5.4.5 or later.

CVE & CISA-KEV Catalog

CVE-2026-40864

MEDIUM

5.4

CVSS v3

NVD

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.

CWE-352Cross-Site Request Forgery

How to fix

Remediation Available

jupyterhubNVD

Affected:>= 4.1.0, < 5.4.5Fixed in:5.4.5CVE-2026-40864derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityLow

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L

Exploit Intelligence

0.16%probability of exploitation in 30 days

5thpercentile

Low risk: more likely to be exploited than 5% of all known CVEs.

References

Patch1

github.com

Vendor Advisory1

github.com

Related Vulnerabilities

Other CWE-352 (Cross-Site Request Forgery) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2016-6277	High	8.8	100%	KEV	-
CVE-2014-0054	Medium	6.8	91%	-	Fix
CVE-2013-6429	Medium	6.8	90%	-	Fix
CVE-2022-41622	High	8.8	88%	-	-
CVE-2018-7700	High	8.8	75%	-	-
CVE-2015-2295	Medium	6.8	66%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-01.