TanStack Router: Unauthenticated reflected XSS in TanStack Start server-function responses

Summary

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.

Timeline

1. Oct 13, 2026, 4:13 PM UTCCVE published
2. Oct 14, 2026, 3:19 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 14, 2026, 3:20 PM UTCRecord last updated

Affected versions

• TanStack router

  fixed in release-2026-09-30-1747

• @tanstack react-start

  From 1.143.12 · fixed in 1.168.60

• @tanstack solid-start

  From 1.143.12 · fixed in 1.168.57

• @tanstack start-server-core

  From 1.143.12 · fixed in 1.169.39

• @tanstack vue-start

  From 1.143.12 · fixed in 1.168.56

• @tanstack/start-server-corenpm

  From 1.143.12 · fixed in 1.169.39

• @tanstack/react-startnpm

  From 1.143.12 · fixed in 1.168.60

• @tanstack/solid-startnpm

  From 1.143.12 · fixed in 1.168.57

• @tanstack/vue-startnpm

  From 1.143.12 · fixed in 1.168.56

References 4