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

> Attackers can execute arbitrary JavaScript in the OAuth server origin via reflected XSS in the GitHub OAuth callback, potentially leading to account takeover.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 17 Apr 2026
- **Updated:** 18 Apr 2026
- **Also known as:** GHSA-4fxq-2x3x-6xqx, GO-2026-5118

## What is CVE-2026-40302?

CVE-2026-40302 is a medium-severity cross-site scripting vulnerability in openziti zrok, published on 17 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation), CWE-116 (Improper Encoding or Escaping of Output)

## Which versions are affected by CVE-2026-40302?

6 open source packages ship an affected version, including github.com/openziti/zrok and github.com/openziti/zrok/v2. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/openziti/zrok` | Go | All versions | None |
| `github.com/openziti/zrok` | Go | All versions to 1.1.11 | None |
| `github.com/openziti/zrok` | Go | All versions to 1.1.11 | None |
| `github.com/openziti/zrok/v2` | Go | All versions | 2.0.1 |
| `github.com/openziti/zrok/v2` | Go | All versions | 2.0.1 |
| `github.com/openziti/zrok/v2` | Go | All versions | 2.0.1 |

Products: Netfoundry Zrok.

## How do I fix CVE-2026-40302?

Upgrade to a fixed version.

## Is CVE-2026-40302 being exploited?

There is no known exploitation of CVE-2026-40302 in the wild and no public exploit code.

## Other vulnerabilities in openziti zrok

- [CVE-2026-45568](https://insights.sbomify.com/CVE-2026-45568/): zrok Python ProxyShare can be used as an SSRF proxy through absolute URL paths (critical 9.9)
- [CVE-2026-42275](https://insights.sbomify.com/CVE-2026-42275/): zrok: WebDAV drive backend follows symlinks outside DriveRoot, enabling host filesystem read/write (high 8.7)
- [CVE-2026-45576](https://insights.sbomify.com/CVE-2026-45576/): zrok copy writes attacker-controlled WebDAV paths outside the destination root (high 8.3)
- [CVE-2026-40303](https://insights.sbomify.com/CVE-2026-40303/): zrok allows unauthenticated DoS via unbounded memory allocation in striped session cookie parsing (high 7.5)
- [CVE-2026-40304](https://insights.sbomify.com/CVE-2026-40304/): zrok's broken ownership check in DELETE /api/v2/unaccess allows non-admin to delete global frontend records (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40302 and fix it if it is affected.

What it is: CVE-2026-40302 is a medium-severity cross-site scripting vulnerability in openziti zrok, published on 17 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-40302 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/openziti/zrok (Go): affected all versions; no fix listed
- github.com/openziti/zrok (Go): affected all versions up to 1.1.11; no fix listed
- github.com/openziti/zrok (Go): affected all versions up to 1.1.11; no fix listed
- github.com/openziti/zrok/v2 (Go): affected all versions; fixed in 2.0.1
- github.com/openziti/zrok/v2 (Go): affected all versions; fixed in 2.0.1
- github.com/openziti/zrok/v2 (Go): affected all versions; fixed in 2.0.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40302/ (Markdown: https://insights.sbomify.com/CVE-2026-40302/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40302
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40302
- OSV: https://osv.dev/vulnerability/CVE-2026-40302

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40302/
Summaries are generated and may contain mistakes; the official description above is the record.