XSS in Netfoundry Zrok
CVE-2026-40302
zrok is software for sharing web services, files, and network resources. Prior to version 2.0.1, the proxyUi template engine uses Go's text/template (which performs no HTML escaping) instead of html/template. The GitHub OAuth callback handlers in both publicProxy and dynamicProxy embed the attacker-controlled refreshInterval query parameter verbatim into an error message when time.ParseDuration fails, and render that error unescaped into HTML. An attacker can deliver a crafted login URL to a victim; after the victim completes the GitHub OAuth flow, the callback page executes arbitrary JavaScript in the OAuth server's origin. Version 2.0.1 patches the issue.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (16.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 16.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
- Netfoundry Zrok
- Openziti Zrok — versions < 2.0.1
Weakness classification (CWE)
References
- github.com/openziti/zrok/security/advisories/GHSA-4fxq-2x3x-6xqx (Vendor Advisory)
- github.com/openziti/zrok/releases/tag/v2.0.1 (Release Notes)
Frequently asked questions
- What is CVE-2026-40302?
- CVE-2026-40302 is a medium-severity vulnerability in Netfoundry Zrok, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-04-17.
- How severe is CVE-2026-40302?
- Medium severity. CVSS v3 base score is 6.1 out of 10.