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

Severity: critical (CVSS 9.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-13 · updated 2026-10-16
Weakness: CWE-79

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.

Affected products

@tanstack react-start: from 1.143.12, < 1.168.60
TanStack router: before release-2026-09-30-1747
@tanstack solid-start: from 1.143.12, < 1.168.57
@tanstack start-server-core: from 1.143.12, < 1.169.39
@tanstack vue-start: from 1.143.12, < 1.168.56

References

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