zrok: Reflected XSS in GitHub OAuth callback via unsanitized refreshInterval error rendering

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-40302: 0.21% estimated exploitation activity in the next 30 days; percentile 11.11 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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. - Attack Vector: Network — the attack is delivered as a crafted URL over the internet. - Attack Complexity: Low — no race conditions or special environment prerequisites. - Privileges Required: None — the attacker needs no account on the zrok instance. - User Interaction: Required — the victim must click the crafted link and complete the GitHub OAuth flow. - Scope: Changed — the injected script executes in the OAuth server's origin, not the victim's…

Published by the source

16 Apr 2026, 21:08 UTC

Last modified by the source

24 Apr 2026, 20:48 UTC

Source last checked

26 Oct 2026, 15:19 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-4fxq-2x3x-6xqx

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# Patch Next advisory brief: CVE-2026-40302

Advisory: zrok: Reflected XSS in GitHub OAuth callback via unsanitized refreshInterval error rendering
IDs: CVE-2026-40302, GHSA-4fxq-2x3x-6xqx
Record: https://patchnext.com/advisories/cve-2026-40302 (revision 1, source checked 26 Oct 2026, 15:19 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/openziti/zrok/v2 2.0.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/openziti/zrok: affected <= 1.1.11
- Go github.com/openziti/zrok/v2: affected < 2.0.1; fixed in 2.0.1

## Suggested inspection (read-only)
- Go github.com/openziti/zrok: check the installed version with your package manager.
- Go github.com/openziti/zrok/v2: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/openziti/zrok, github.com/openziti/zrok/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-4fxq-2x3x-6xqx (GitHub-reviewed advisory GHSA-4fxq-2x3x-6xqx lists affected ranges: Go github.com/openziti/zrok >=0 =0 <2.0.1)

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