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

- Exploited (CISA KEV): no
- Published: 2026-10-13
- CVSS: 9.3 CRITICAL (v3.1)
- EPSS: 0.5% (46th percentile)
- CWE: CWE-79

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.

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Blocks by default | 2026-10-12 | -1 |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | No public claim | — | — |
| Fastly | No public claim | — | — |
| F5 | No public claim | — | — |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

### Cloudflare

- 2026-10-12 · new · rule 22220c5e2682463daa5536214ee560b2 · default Block
  > TanStack - Reflected XSS - CVE:CVE-2026-102989. Previous action: N/A. New action: Block. This is a new detection.
  Source: https://developers.cloudflare.com/changelog/post/2026-10-12-waf-release/

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2026-102989 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2026-102989