How severe is CVE-2026-40303?

CVE-2026-40303 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-40303 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (36th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40303?

CVE-2026-40303 affects Netfoundry Zrok. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-40303?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-40303 have an EU (EUVD) identifier?

Yes. CVE-2026-40303 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-23550.

When was CVE-2026-40303 published?

CVE-2026-40303 was published on 2026-04-17 and last updated on 2026-06-17.

CVE-2026-40303

CVE-2026-40303 is a high-severity vulnerability in Netfoundry Zrok with a CVSS 3.x base score of 7.5. 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-400.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (36th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-23550
Weakness: CWE-400
Affected product: Netfoundry Zrok
Published: 2026-04-17
Last modified: 2026-06-17

Description

zrok is software for sharing web services, files, and network resources. Prior to version 2.0.1, endpoints.GetSessionCookie parses an attacker-supplied cookie chunk count and calls make([]string, count) with no upper bound before any token validation occurs. The function is reached on every request to an OAuth-protected proxy share, allowing an unauthenticated remote attacker to trigger gigabyte-scale heap allocations per request, leading to process-level OOM termination or repeated goroutine panics. Both publicProxy and dynamicProxy are affected. Version 2.0.1 patches the issue.

Frequently asked questions

What is CVE-2026-40303?: zrok is software for sharing web services, files, and network resources. Prior to version 2.0.1, endpoints.GetSessionCookie parses an attacker-supplied cookie chunk count and calls make([]string, count) with no upper bound before any token validation occurs. The function is reached on every request to an OAuth-protected proxy share, allowing an unauthenticated remote attacker to trigger gigabyte-scale heap allocations per request, leading to process-level OOM termination or repeated goroutine panics. Both publicProxy and dynamicProxy are affected. Version 2.0.1 patches the issue.
How severe is CVE-2026-40303?: CVE-2026-40303 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-40303 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (36th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-40303?: CVE-2026-40303 affects Netfoundry Zrok. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-40303?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-40303 have an EU (EUVD) identifier?: Yes. CVE-2026-40303 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-23550.
When was CVE-2026-40303 published?: CVE-2026-40303 was published on 2026-04-17 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:netfoundry:zrok:*:*:*:*:*:*:*:*

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