{"id":"CVE-2026-84428","revision":"49d5ac422c204fe4bf113e429822fe4c","records":[{"revision":"49d5ac422c204fe4bf113e429822fe4c","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-84428","aliases":[],"title":"fastify vulnerable to header validation bypass via incomplete schema case normalization","description":"fastify versions before 5.12.2 implement the case-insensitive nature of HTTP header names by lowercasing names in a route's header schema before compiling it, but the transformation is incomplete: it lowercases the properties keys and the root-level required array, and does not lowercase the trigger and dependent names inside the JSON Schema Draft 7 dependencies keyword. Because Node stores request header names in lowercase, a canonical-case dependency such as requiring an authentication header whenever a privileged-mode header is present never matches, and the presence assertion is silently skipped. An unauthenticated remote client can therefore send the header that activates a privileged branch while omitting the header the dependency was meant to require, bypassing the conditional check. Users should upgrade to fastify 5.12.2 or later.","state":0,"publishedAt":"2026-09-04T10:24:27.809+00:00","modifiedAt":"2026-09-04T16:06:04.123+00:00","affected":[{"ecosystem":"Vendor product","name":"fastify","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"fastify\",\n                    \"product\": \"fastify\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"versions\": [\n                        {\n                            \"versionType\": \"semver\",\n                            \"status\": \"affected\",\n                            \"version\": \"0\",\n                            \"lessThan\": \"5.12.2\"\n                        },\n                        {\n                            \"versionType\": \"semver\",\n                            \"status\": \"unaffected\",\n                            \"version\": \"5.12.2\"\n                        }\n                    ],\n                    \"packageURL\": \"pkg:npm/fastify\"\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","score":7.5,"severity":"HIGH"}],"references":["https://github.com/fastify/fastify/security/advisories/GHSA-9q9j-q6p8-xq58","https://cna.openjsf.org/security-advisories.html"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-84428","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-84428","identifiers":["CVE-2026-84428"]},"retained":false,"historicalAffected":[]}],"coverage":[]}