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CVE-2026-14198

@fastify/middie vulnerable to authorization bypass via encoded slash in path parameter values

CVSS 9.1 CRITICALCWE-436
Vexday Risk Score
25Baixo
Decisão SSVC (CISA)
Track
Sem sinal de exploração → monitorar
CVSS 9.1EPSS KEV nãoPoC Nuclei Metasploit Patch
Ciclo de vida
01 jul 2026Publicada no NVD
Recomendação: Monitorar — sem sinal de exploração no momento.
@fastify/middie versions 9.1.0 through 9.3.2 decode the encoded slash %2F inside path parameter values before matching middleware paths, while Fastify's underlying router preserves the encoding during route lookup. The two layers disagree on the canonical request path, so the middleware fails to match a URL that the route handler does match. When middleware is used for authentication, authorization, rate limiting, or auditing on parameterized paths, an attacker can reach the protected handler by sending a single crafted URL with an encoded slash in the parameter position. The bypass is HTTP method agnostic and requires no authentication or special preconditions. Patches: upgrade to @fastify/middie 9.3.3. Workarounds: avoid parameterized middleware paths for security decisions, or enforce authentication at the route handler or via a Fastify hook that runs after the router has resolved the request.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N