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.
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Affected Vendors & Products
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References
History
Fri, 04 Sep 2026 12:45:00 +0000
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| First Time appeared |
Fastify
Fastify fastify |
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| Vendors & Products |
Fastify
Fastify fastify |
Fri, 04 Sep 2026 12:15:00 +0000
| Type | Values Removed | Values Added |
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| Weaknesses | CWE-1287 | |
| References |
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| Metrics |
threat_severity
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threat_severity
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Fri, 04 Sep 2026 10:15:00 +0000
| Type | Values Removed | Values Added |
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| 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 |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: openjs
Published:
Updated: 2026-09-04T19:34:13.735Z
Reserved: 2026-09-01T20:07:12.965Z
Link: CVE-2026-84469
No data.
Status : Received
Published: 2026-09-04T10:17:13.677
Modified: 2026-09-04T20:17:30.483
Link: CVE-2026-84469
OpenCVE Enrichment
Updated: 2026-09-04T15:00:05Z