CVE-2026-84428 - fastify vulnerable to header validation bypass via incomplete schema case normalization

CVE-2026-84428 - fastify vulnerable to header validation bypass via incomplete schema case normalization

https://cvefeed.io/rssfeed/latest.atom / Fri, 09/04/2026 - 13:30
CVE ID :CVE-2026-84428
Published : Sept. 4, 2026, 10:24 a.m. | 39 minutes ago
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.
Severity: 7.5 | HIGH
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