fastify vulnerable to header validation bypass via incomplete schema case normalization — GHSA-9Q9J-Q6P8-XQ58

Summary

### Impact Fastify lowercases header-schema property names before compiling the schema, because Node.js stores request header names in lowercase. That normalization was incomplete: it lowercased only top-level `properties` keys and the root `required` array, and did not lowercase the JSON Schema Draft 7 `dependencies` keyword (its trigger keys and dependent property names) or names in nested subschemas. As a…

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: 0.00524.
• 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-9Q9J-Q6P8-XQ58

Source

GitHub

Vendor

GitHub

Published by source

2026-09-30

Last source activity

2026-09-30

Additional identifiers

CVE-2026-84428

Curated by

hlukh.ch

Related advisories and connections

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