CVE-2026-84469

fastify vulnerable to request validation bypass via skipped boolean false schemas

Published Sep 4, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
fastify versions before 5.12.2 decide whether to compile a request schema based on JavaScript truthiness, but JSON Schema Draft 7 defines the boolean false as a valid schema that rejects every instance. When an application assigns false to a route's body, querystring, params, or headers schema to deny all input, fastify treats it as a missing schema, compiles no validator, and runs the route handler on any request. An unauthenticated remote client can therefore reach a handler that a valid deny-all schema was intended to make unreachable, a complete validation bypass that can lead to unauthorized state changes or execution of disabled operations. Users should upgrade to fastify 5.12.2 or later.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-hwr6-493r-vm6h fastify vulnerable to request validation bypass via skipped boolean false schemas
History
Type Values Removed Values Added
CPEs cpe:2.3:a:fastify:fastify:*:*:*:*:*:node.js:*:*
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Fastify
Fastify fastify
Vendors & Products Fastify
Fastify fastify
Type Values Removed Values Added
Description fastify versions before 5.12.2 decide whether to compile a request schema based on JavaScript truthiness, but JSON Schema Draft 7 defines the boolean false as a valid schema that rejects every instance. When an application assigns false to a route's body, querystring, params, or headers schema to deny all input, fastify treats it as a missing schema, compiles no validator, and runs the route handler on any request. An unauthenticated remote client can therefore reach a handler that a valid deny-all schema was intended to make unreachable, a complete validation bypass that can lead to unauthorized state changes or execution of disabled operations. Users should upgrade to fastify 5.12.2 or later.
Title fastify vulnerable to request validation bypass via skipped boolean false schemas
Weaknesses CWE-20
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
openjs
Published
Updated
Sep 4, 2026, 7:34 PM
Reserved
Sep 1, 2026, 8:07 PM
Status
Analyzed
Published
Sep 4, 2026, 10:17 AM
Modified
Sep 15, 2026, 8:06 PM
Severity
Important
Public date
Sep 4, 2026, 9:59 AM