Is CVE-2026-40304 in the CISA KEV catalog?

No. CVE-2026-40304 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-40304?

CVE-2026-40304 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2026-40304?

CVE-2026-40304 has an EPSS score of 0.29% (20th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-40304?

Upgrade zrok to 2.0.1 or later.

CVE & CISA-KEV Catalog

CVE-2026-40304

MEDIUM

5.3

CVSS v3

NVD

Description

zrok is software for sharing web services, files, and network resources. Prior to version 2.0.1, the unaccess handler (controller/unaccess.go) contains a logical error in its ownership guard: when a frontend record has environment_id = NULL (the marker for admin-created global frontends), the condition short-circuits to false and allows the deletion to proceed without any ownership verification. A non-admin user who knows a global frontend token can call DELETE /api/v2/unaccess with any of their own environment IDs and permanently delete the global frontend, taking down all public shares routed through it. Version 2.0.1 patches the issue.

CWE-284Improper Access Control CWE-863Incorrect Authorization

How to fix

Remediation Available

zrokNVD

Affected:< 2.0.1Fixed in:2.0.1CVE-2026-40304derived 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 ComplexityHigh

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

0.29%probability of exploitation in 30 days

20thpercentile

Low risk: more likely to be exploited than 20% of all known CVEs.

References

Vendor Advisory1

github.com

Release Notes1

github.com

Related Vulnerabilities

Other CWE-284 (Improper Access Control) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-27350	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2019-1653	High	7.5	100%	KEV	-
CVE-2023-23752	Medium	5.3	100%	KEV	Fix
CVE-2023-29298	High	7.5	100%	KEV	-
CVE-2023-38205	High	7.5	100%	KEV	-
CVE-2024-27348	Critical	9.8	99%	KEV	Fix

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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 2026-04-23.