Fastify's Missing End Anchor in "subtypeNameReg" Allows Malformed Content-Types to Pass Validation
Description
Fastify incorrectly accepts malformed Content-Type headers containing trailing characters after the subtype token, in violation of RFC 9110 §8.3.1. For example, a request sent with Content-Type: application/json garbage passes validation and is processed normally, rather than being rejected with 415 Unsupported Media Type.
When regex-based content-type parsers are in use (a documented Fastify feature), the malformed value is matched against registered parsers using the full string including the trailing garbage. This means a request with an invalid content-type may be routed to and processed by a parser it should never have reached.
Impact
An attacker can send requests with RFC-invalid Content-Type headers that bypass validity checks, reach content-type parser matching, and be processed by the server. Requests that should be rejected at the validation stage are instead handled as if the content-type were valid.
Workarounds
Deploy a WAF rule to protect against this
Fix
The fix is available starting with v5.8.1.
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Paquete de npm | fastify | >= 5.7.2, < 5.8.1 | 5.8.1 |
Referencias
- https://github.com/fastify/fastify/security/advisories/GHSA-573f-x89g-hqp9
- https://nvd.nist.gov/vuln/detail/CVE-2026-3419
- https://github.com/fastify/fastify/commit/67f6c9b32cb3623d3c9470cc17ed830dd2f083d7
- https://cna.openjsf.org/security-advisories.html
- https://github.com/advisories/GHSA-573f-x89g-hqp9
- https://github.com/fastify/fastify
- https://httpwg.org/specs/rfc9110.html#field.content-type
- https://www.cve.org/CVERecord?id=CVE-2026-3419
- Vector CVSS
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N- Debilidad (CWE)
CWE-185- Plataforma
- npm
- Paquete
fastify- Publicada
- 05.03.2026
- Actualizado
- 11.10.2026 10:22
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-573f-x89g-hqp9 - 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
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