SEPTEMBER 17, 2026
Live Feed
Back to database
Case File

CVE-2026-84504

HIGH · CVSS 8.1 EPSS 0.40% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-09-04 · Last synced 2026-09-17

CyberRota Analysis

AI-Generated

Fastify versions prior to 5.12.2 are vulnerable to a flaw where an authenticated low-privilege user can manipulate request bodies by exploiting the handling of properties named "value," potentially leading to unauthorized state changes and data disclosure. This vulnerability allows attackers to bypass route schema validations, resulting in significant security risks. Organizations using affected Fastify versions should prioritize upgrading to 5.12.2 or later to mitigate these risks.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

GitHub PoC Links

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-84504
Severity
HIGH
CVSS
8.1
EPSS
0.40%

Original NVD Description

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.

Related CVEs

Other vulnerabilities affecting the same vendor(s)