fkie_cve-2026-102989

TanStack Router is a client-first, server-capable, fully type-safe router and full-stack framework for the web. From 1.143.12 until 1.169.39 for @tanstack/start-server-core, 1.168.60 for @tanstack/react-start, 1.168.57 for @tanstack/solid-start, and 1.168.56 for @tanstack/vue-start, an unauthenticated attacker can place non-public fields in a server-function request payload so that attacker-controlled middleware state reaches the error path and a response-shaped object is accepted as an HTTP response. A crafted server-function URL can therefore return attacker-controlled HTML from the application's origin; when a visitor opens the URL, the injected script can access same-origin data and issue requests with the visitor's authority. This issue is fixed in @tanstack/start-server-core 1.169.39, @tanstack/react-start 1.168.60, @tanstack/solid-start 1.168.57, and @tanstack/vue-start 1.168.56.

GHSA-qx66-fv34-fjm8 — TanStack Router: Unauthenticated reflected XSS in TanStack Start server-function responses

Affected: npm: @tanstack/start-server-core, npm: @tanstack/react-start, npm: @tanstack/solid-start, npm: @tanstack/vue-start

## Impact

An unauthenticated attacker can craft a URL to a server function in an affected TanStack Start app. If someone opens the link, the app can return attacker-controlled HTML from its own origin and run the attacker's JavaScript there. The script can access same-origin data available to that visitor and make requests with their authority.

## Cause

The server-function transport can pass request payload fields into internal middleware state instead of limiting them to public input fields. A malformed payload can leave an attacker-controlled result in the error path. Response handling can then treat a response-shaped object as an HTTP response.

## Affected versions

Published versions of `@tanstack/start-server-core`, `@tanstack/react-start`, `@tanstack/solid-start`, and `@tanstack/vue-start` from `1.143.12` up to, but not including, their respective patched versions are affected. The patched versions are `@tanstack/start-server-core@1.169.39`, `@tanstack/react-start@1.168.60`, `@tanstack/solid-start@1.168.57`, and `@tanstack/vue-start@1.168.56`.

## Fix

The fix limits client-supplied server-function input to public fields and validates responses at the server boundary. Upgrade to the corresponding patched package version.

## Temporary mitigations

For the configured server-function path, usually `/_serverFn/*`, an edge or WAF rule can consider blocking requests without the literal `x-tsr-serverFn: true` header and browser document navigations such as `Sec-Fetch-Mod…

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fkie_cve-2026-102989

GHSA-qx66-fv34-fjm8 — TanStack Router: Unauthenticated reflected XSS in TanStack Start server-function responses