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

@tanstack/start-server-core (npm), @tanstack/react-start (npm), @tanstack/solid-start (npm), @tanstack/vue-start (npm)

## 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…

First seen: 15 Oct 2026
Last update: 15 Oct 2026, 20:22 UTC
Fixed in: @tanstack/start-server-core 1.169.39
@tanstack/react-start 1.168.60
@tanstack/solid-start 1.168.57
@tanstack/vue-start 1.168.56
Identifiers: CVE-2026-102989
CVSS: 9.3
Source: GitHub advisory
On the menu as: npm packages
React

Check this repository for exposure to one security incident from pwned.coffee. Report first, change nothing until I say so.

## TanStack Router: Unauthenticated reflected XSS in TanStack Start server-function responses
Severity: critical. Patch status: patched.
Affected: @tanstack/start-server-core (npm), @tanstack/react-start (npm), @tanstack/solid-start (npm), @tanstack/vue-start (npm)
Fixed in: @tanstack/start-server-core 1.169.39, @tanstack/react-start 1.168.60, @tanstack/solid-start 1.168.57, @tanstack/vue-start 1.168.56
Ids: CVE-2026-102989

## 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…

## Steps
1. Search every lockfile and manifest (package-lock.json, yarn.lock, pnpm-lock.yaml, requirements*.txt, poetry.lock, uv.lock, composer.lock, go.sum, Cargo.lock, Gemfile.lock) for `@tanstack/start-server-core`, `@tanstack/react-start`, `@tanstack/solid-start`, `@tanstack/vue-start`. For each hit, compare the installed version with the fix on the same major line: @tanstack/start-server-core 1.169.39, @tanstack/react-start 1.168.60, @tanstack/solid-start 1.168.57, @tanstack/vue-start 1.168.56. If it's lower, give the exact upgrade command for the package manager this repo uses.

## Report
A table: file, product or package, version in use, affected yes/no, exact fix. Then anything a human has to check outside the repo.

If you have the pwned.coffee MCP server (https://pwned.coffee/mcp), call lookup_cve("CVE-2026-102989") for the latest, and check_repo with this repo's lockfiles, Dockerfiles and workflows for a full receipt.
Sources: https://github.com/TanStack/router/commit/d521abd71c69f1ff010bb3def4d417cb5fa058cb https://github.com/TanStack/router/pull/8573 https://github.com/TanStack/router/security/advisories/GHSA-qx66-fv34-fjm8 https://github.com/advisories/GHSA-qx66-fv34-fjm8 https://nvd.nist.gov/vuln/detail/CVE-2026-102989
https://pwned.coffee/i/tanstack-router-unauthenticated-reflected-xss-in-tanstac-cve-2026-102989

Sources

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