fastify vulnerable to X-Forwarded-* spoofing under trustProxy hop-count
Impact
The fix for CVE-2026-3635 (GHSA-444r-cwp2-x5xf) added a proxyFn(socket.remoteAddress, 0) guard on the X-Forwarded-* reads in request.host, request.protocol, request.hostname, request.ip, and request.ips. That guard closes the IP, CIDR, and custom-function forms of trustProxy correctly because those forms compile to predicates that inspect the connecting address. The hop-count form (trustProxy: <number>) compiles to a predicate that structurally ignores the address argument, so the guard reduces to 0 < tp, always true for any tp >= 1.
Applications configured with trustProxy: <number> (documented as "behind N reverse proxies", trustProxy: 1 being the canonical single-proxy setting) remain vulnerable. An attacker who can reach the Fastify origin directly, bypassing the front-facing proxy, can spoof the request fields exactly as in the unpatched version. Impact class matches the parent CVE-2026-3635: host injection in generated URLs, HTTPS-enforcement bypass, secure-cookie / CSRF-origin bypass, host-based routing and cache poisoning.
Patches
Patched in fastify 5.12.1. The numeric form of trustProxy is now disabled at runtime and removed from the TypeScript type union.
Workarounds
- Migrate to an IP / CIDR / custom-function
trustProxyvalue that validates the connecting address. Custom functions must inspect theaddressargument, not only the hop index. - Ensure the Fastify origin is only reachable through the trusted proxy chain (no direct network path).
Software afectado
Haz clic en una tecnología para ver todas sus vulnerabilidades.
| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Paquete de npm | fastify | >= 5.8.3, < 5.12.1 | 5.12.1 |
Referencias
- https://github.com/fastify/fastify/security/advisories/GHSA-3m5p-2c4r-xxw2
- https://nvd.nist.gov/vuln/detail/CVE-2026-16732
- https://github.com/fastify/fastify/commit/8acfea7eada05383a7357e3eb21c2628416df280
- https://cna.openjsf.org/security-advisories.html
- https://github.com/fastify/fastify
- https://github.com/fastify/fastify/releases/tag/v5.12.1
- Vector CVSS
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N- Debilidad (CWE)
CWE-348- Plataforma
- npm
- Paquete
fastify- Publicada
- 02.09.2026
- Actualizado
- 11.10.2026 10:22
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-3m5p-2c4r-xxw2 - CC BY 4.0
Historial de vulnerabilidades: fastify
Todas las vulnerabilidades publicadas de este paquete (Paquete de npm), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 16
- Primera → última
- 07.2018 09.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Alta 8
- Media 7
- Baja 1
Divulgaciones por año
- 2018: 1
- 2019: 0
- 2020: 1
- 2021: 0
- 2022: 2
- 2023: 0
- 2024: 0
- 2025: 1
- 2026: 11
-
fastify vulnerable to X-Forwarded-* spoofing under trustProxy hop-count esta entrada
Identifica las vulnerabilidades de tu aplicación
Con la integración de DockRay y el inventario de software activado, DockRay compara las versiones notificadas de los componentes con las vulnerabilidades conocidas y avisa de las coincidencias confirmadas. La cobertura depende de la tecnología compatible y de los avisos disponibles.