fastify vulnerable to request validation bypass via skipped boolean false schemas — GHSA-HWR6-493R-VM6H

Summary

### Impact Fastify decided whether to validate a request part by checking its schema for JavaScript truthiness. JSON Schema Draft 7 defines the boolean `false` as a valid schema that rejects every instance, but because `false` is falsy, a route that set `body`, `querystring`, `params`, or `headers` to `false` had that part left uncompiled: no validator was attached and the request reached the handler. An…

Timeline

Published by source

2026-09-30

Risk context

• Reported severity or threat level: high.
• Reported CVSS score: 7.5 out of 10.
• Reported EPSS value: 0.00492.
• Review exposure for the affected product or family: npm: fastify.

Product

npm: fastify

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-HWR6-493R-VM6H

Source

GitHub

Vendor

GitHub

Published by source

2026-09-30

Last source activity

2026-09-30

Additional identifiers

CVE-2026-84469

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.