How severe is GHSA-4fxq-2x3x-6xqx?

GHSA-4fxq-2x3x-6xqx has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-4fxq-2x3x-6xqx?

GHSA-4fxq-2x3x-6xqx affects the following packages: github.com/openziti/zrok (Go), github.com/openziti/zrok/v2 (Go). Ecosystems affected: Go.

How do I fix GHSA-4fxq-2x3x-6xqx?

No patched version of github.com/openziti/zrok has shipped for GHSA-4fxq-2x3x-6xqx yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

How do I detect GHSA-4fxq-2x3x-6xqx in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/openziti/zrok. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-4fxq-2x3x-6xqx if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-4fxq-2x3x-6xqx?

O3 pinpoints whether GHSA-4fxq-2x3x-6xqx is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-4fxq-2x3x-6xqx actively exploited in the wild?

No public exploit code has been indexed for GHSA-4fxq-2x3x-6xqx yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-4fxq-2x3x-6xqx?

GHSA-4fxq-2x3x-6xqx has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 11th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was GHSA-4fxq-2x3x-6xqx published, and has it been updated?

GHSA-4fxq-2x3x-6xqx was published on April 16, 2026 and was last updated on June 25, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

GHSA-4fxq-2x3x-6xqx

MEDIUM

GHSA-4fxq-2x3x-6xqx is a medium-severity (CVSS 6.1) vulnerability in github.com/openziti/zrok. O3 Security confirms whether GHSA-4fxq-2x3x-6xqx is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

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

Also known asCVE-2026-40302GO-2026-5118

Published

Apr 16, 2026

Updated

Jun 25, 2026

Affected

2 pkgs

Patched

1 / 2

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs11th percentile — riskier than 11% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

2 pkgs affected

🐹github.com/openziti/zrok🐹github.com/openziti/zrok/v2

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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 share origin.
Confidentiality Impact: Low — the script runs in the OAuth server origin after a failed flow; no session cookie is set at this point, limiting what can be exfiltrated to what is visible in the DOM and what can be requested from the OAuth server.
Integrity Impact: Low — the script can initiate new OAuth flows or submit forms on behalf of the victim in the OAuth server origin.
Availability Impact: None.

Affected Components

endpoints/proxyUi/template.go — init() / WriteTemplate (lines 8, 18, 99) — text/template used for HTML rendering
endpoints/proxyUi/template.html — line 119 — {{ .Error }} in HTML without escaping
endpoints/publicProxy/providerGithub.go — login callback closure (lines 93, 128, 130)
endpoints/dynamicProxy/providerGithub.go — loginHandler() (lines 110, 146, 148)

Affected Packages

2 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/openziti/zrok`	all versions	No fix
🐹Go	`github.com/openziti/zrok/v2`	all versions	2.0.1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/openziti/zrok. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
No patched version of github.com/openziti/zrok has shipped for GHSA-4fxq-2x3x-6xqx yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-4fxq-2x3x-6xqx is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-4fxq-2x3x-6xqx. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

**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

O3 Security · Impact-Aware SCA

Is GHSA-4fxq-2x3x-6xqx in your dependencies?

O3 detects GHSA-4fxq-2x3x-6xqx across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works