CVE-2026-84504High· 8.1▾ Twilightfastify versions before 5.12.2 treat the object resolved by a successful Ajv async validator as the value result protocol used by custom validator compilers. If a request that passes its route schema contains a property named value at th…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 44.6 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Sep 8.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
0.4%
Last analysed / modified upstream
0.4% → 0.4%
fastify versions before 5.12.2 treat the object resolved by a successful Ajv async validator as the value result protocol used by custom validator compilers. If a request that passes its route schema contains a property named value at the root, fastify replaces the entire request body with that property's value before the handler runs, so the handler receives a different object than the one that satisfied the schema. An authenticated low-privilege caller can use this to make nested data replace the validated body and trigger an operation the route schema did not authorize, leading to unauthorized state changes and data disclosure. Users should upgrade to fastify 5.12.2 or later.
fastify < 5.12.2Upgrade past the affected range:
fastify 5.12.2Connected by shared product, vendor, weakness, or advisory.
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CVE-2026-92081Medium· 5.9fastify is a fast and low-overhead web framework for Node.js
CVE-2026-76169High· 7.5fastify 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
CVE-2026-84428High· 7.5fastify versions before 5.12.2 implement the case-insensitive nature of HTTP header names by lowercasing names in a route's header schema before compiling it, but the transformation is incomplete: it lowercases the properties keys and th…
CVE-2026-25223High· 7.5Fastify is a fast and low overhead web framework, for Node.js
CVE-2026-18504Medium· 5.4fastify vulnerable to schema validation bypass via root primitive coercion mismatch