---
title: "TanStack Start XSS vulnerability: what Netlify users need to know"
description: "A critical reflected XSS in TanStack Start server functions has been disclosed. Affected apps should upgrade to patched releases."
source: "https://www.netlify.com/changelog/2026-09-30-tanstack-start-security-vulnerability/"
last_updated: "2026-10-01T06:52:31.000Z"
---
The TanStack team has disclosed a critical [cross-site scripting (XSS) vulnerability](https://github.com/TanStack/router/security/advisories/GHSA-qx66-fv34-fjm8) in TanStack Start. A crafted URL can cause an affected app to return attacker-controlled HTML from its own origin, which may run attacker-supplied JavaScript in a visitor’s browser. Here’s what Netlify customers need to know.

## Vulnerabilities

[**GHSA-qx66-fv34-fjm8**](https://github.com/TanStack/router/security/advisories/GHSA-qx66-fv34-fjm8) ([CVE-2026-102989](https://www.cve.org/CVERecord?id=CVE-2026-102989)): Unauthenticated reflected XSS in server-function responses.

Package

Affected versions

Fixed in

`@tanstack/react-start`

\>= 1.143.12, < 1.168.60

1.168.60

`@tanstack/solid-start`

\>= 1.143.12, < 1.168.57

1.168.57

`@tanstack/vue-start`

\>= 1.143.12, < 1.168.56

1.168.56

`@tanstack/start-server-core`

\>= 1.143.12, < 1.169.39

1.169.39

## Impact on Netlify

This is a client-side cross-site scripting (XSS) vulnerability in TanStack Start’s server-function response handling. Because the malicious response is returned from the app’s own origin, an attacker who gets a victim to open a crafted link can run JavaScript in that visitor’s session — for example, to read their data or act as them on the site. All applications on an affected version should upgrade.

## What should I do?

We strongly recommend upgrading as soon as possible to the patched releases:

-   `@tanstack/react-start` 1.168.60 or later
-   `@tanstack/solid-start` 1.168.57 or later
-   `@tanstack/vue-start` 1.168.56 or later
-   `@tanstack/start-server-core` 1.169.39 or later

### Not sure if you’re affected?

Open your project in [Agent Runners](https://docs.netlify.com/build/build-with-ai/agent-runners/overview/) in [ask mode](https://www.netlify.com/blog/agent-runners-ask-mode/) and try this prompt:

``Does this project use TanStack Start? If so, which versions of `@tanstack/react-start`, `@tanstack/solid-start`, `@tanstack/vue-start`, and `@tanstack/start-server-core` are resolved in the lockfile? Is the resolved `@tanstack/start-server-core` version 1.169.39 or later? If not, what do I need to change to upgrade? (Advisory: GHSA-qx66-fv34-fjm8)``

Ask mode answers without changing your code. If an upgrade is needed, switch to Build mode to make the change, preview, and redeploy.

### Deploy previews and branch deploys

Note that any publicly available deploy previews and branch deploys may remain vulnerable until they are [automatically deleted](https://docs.netlify.com/deploy/manage-deploys/manage-deploys-overview/#automatic-deploy-deletion). Consider [deleting these deploys manually](https://docs.netlify.com/deploy/manage-deploys/manage-deploys-overview/#manual-deploy-deletion-through-the-netlify-ui).

## Resources

-   [GitHub security advisory (GHSA-qx66-fv34-fjm8)](https://github.com/TanStack/router/security/advisories/GHSA-qx66-fv34-fjm8)
-   [TanStack security update: CVE-2026-102989](https://tanstack.com/blog/tanstack-start-security-update-cve-2026-102989)
-   [CVE-2026-102989](https://www.cve.org/CVERecord?id=CVE-2026-102989)