CVE-2026-40303

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.

CVSS v3.1 Score

7.5

HIGH

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

EPSS — Exploit Prediction

0.0003

Probability of exploitation

0.08%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-400 Uncontrolled Resource Consumption

CWE-789 CWE-789

Affected Products

Vendor	Product	Versions
netfoundry	zrok	< 2.0.1

References

Advisories & Patches

https://github.com/openziti/zrok/security/advisories/GHSA-cpf9-ph2j-ccr9

Other References

https://github.com/openziti/zrok/releases/tag/v2.0.1

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-40303? +

CVE-2026-40303 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0003, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-40303? +

CVE-2026-40303 affects products from netfoundry, specifically: zrok. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-40303? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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