CVE-2026-84469
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 …
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | fastify | < 5.12.2 | 5.12.2 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Fastify | Fastify | before 5.12.2 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-hwr6-493r-vm6h
- https://github.com/fastify/fastify/security/advisories/GHSA-hwr6-493r-vm6h
- https://nvd.nist.gov/vuln/detail/CVE-2026-84469
- https://github.com/fastify/fastify/commit/7de6e81697778f9f41bd327a3b1c5c9a0d9637b4
- https://cna.openjsf.org/security-advisories.html
- https://github.com/fastify/fastify/releases/tag/v5.12.2