← CVE Intelligence

CVE-2026-84428

fastify vulnerable to header validation bypass via incomplete schema case normalization PUBLISHED

Description (CNA)

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.

Affected (CNA)

Vendor / productVersions
fastify / fastifyaffected 0 before 5.12.2; unaffected 5.12.2

CWE

CWE-178

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.