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.
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Fri, 04 Sep 2026 12:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Fastify
Fastify fastify |
|
| Vendors & Products |
Fastify
Fastify fastify |
Fri, 04 Sep 2026 12:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-1287 | |
| References |
| |
| Metrics |
threat_severity
|
threat_severity
|
Fri, 04 Sep 2026 10:15:00 +0000
| 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
|
Projects
Sign in to view the affected projects.
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: 2026-09-04T10:17:13.677
Link: CVE-2026-84469
OpenCVE Enrichment
Updated: 2026-09-04T15:00:05Z