CVE-2026-3419— Fastify's Missing End Anchor in "subtypeNameReg" Allows Malformed Content-Types to Pass Validation

Fastify's Missing End Anchor in "subtypeNameReg" Allows Malformed Content-Types to Pass Validation

Fastify incorrectly accepts malformed `Content-Type` headers containing trailing characters after the subtype token, in violation of RFC 9110 §8.3.1(https://httpwg.org/specs/rfc9110.html#field.content-type). 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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

不正确的正则表达式

Fastify 安全漏洞

Fastify是Fastify开源的一个 Web 框架。 Fastify存在安全漏洞，该漏洞源于错误接受格式错误的Content-Type标头，可能导致攻击者发送绕过有效性检查的请求并被服务器处理。

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