CyberRota Analysis
AI-GeneratedFastify versions 4.0.0 to 5.12.1 are vulnerable to a flaw that allows unauthenticated attackers to bypass authentication mechanisms and access protected resources by exploiting malformed URLs routed through sibling plugins. This vulnerability compromises prefix encapsulation, enabling attackers to read sensitive responses from private handlers. Organizations using affected Fastify versions should prioritize upgrading to 5.12.2 or later to mitigate this risk.
Public Exploit Signal
A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.
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Original NVD Description
fastify versions >= 4.0.0 and before 5.12.2 can route a malformed URL sent under one plugin prefix to the custom not-found handler of a different sibling plugin, and invoke it without the preHandler hook declared for that handler. The internal not-found router for encapsulated handlers dispatches malformed paths through a single shared handler pointer before URL decoding, ignoring the prefix and skipping the selected handler's normal lifecycle. An unauthenticated attacker can therefore reach an authentication-protected private fallback through an unrelated public prefix and read its full response, bypassing the authentication hook and breaking prefix encapsulation. Users should upgrade to fastify 5.12.2 or later.
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