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CVE-2026-40302: zrok has reflected XSS in GitHub OAuth callback via unsanitized refreshInterval error rendering

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-17 · updated 2026-10-26
• Weakness: CWE-79

Description

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.

Affected products

• openziti zrok: before 2.0.1 — fixed in 2.0.1

How to fix

Upgrade to a fixed version: openziti zrok 2.0.1. Check the vendor advisory for mitigations.

References

• https://github.com/openziti/zrok/releases/tag/v2.0.1
• https://github.com/openziti/zrok/security/advisories/GHSA-4fxq-2x3x-6xqx

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