{"id":"CVE-2026-84428","title":"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 th…","summary":"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 th…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","cwe":["CWE-178","CWE-1289"],"vendor":"fastify","product":"fastify","affected":["fastify < 5.12.2"],"patched":["fastify 5.12.2"],"published":"2026-09-04","updated":"2026-09-15","sourceUpdated":"2026-09-15T19:54:32.420","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-84428","references":[{"url":"https://cna.openjsf.org/security-advisories.html","label":"ce714d77-add3-4f53-aff5-83d477b104bb"},{"url":"https://github.com/fastify/fastify/security/advisories/GHSA-9q9j-q6p8-xq58","label":"ce714d77-add3-4f53-aff5-83d477b104bb"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-84428.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-84428"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2528468"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-84428"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-84428"},{"url":"https://github.com/fastify/fastify/commit/179619c8e99d54924309b9933402151ef9af37e0"},{"url":"https://github.com/fastify/fastify/releases/tag/v5.12.2"},{"url":"https://github.com/advisories/GHSA-9q9j-q6p8-xq58"},{"url":"https://access.redhat.com/errata/RHSA-2026:84734"}],"tags":["nvd","csaf","vex","red-hat","ghsa","npm"],"epss":0.00524,"epssPercentile":0.44276,"ingestedAt":"2026-09-08T19:08:49.592Z","aliases":["GHSA-9q9j-q6p8-xq58"],"ecosystem":"npm","slug":"CVE-2026-84428","body":"## Overview\n\nfastify 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.\n\n## Affected\n\n- `fastify < 5.12.2`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `fastify 5.12.2`\n\n## Vendor advisories\n\n- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat OpenShift AI (RHOAI), Red Hat OpenShift Dev Spaces · no fix planned: Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat OpenShift AI (RHOAI), Red Hat OpenShift Dev Spaces · updated 2026-10-19 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-84428.json)\n- **RHSA-2026:84734** · Red Hat · fixed in: Red Hat OpenShift AI 3.4 · released 2026-10-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:84734)\n\n## Package advisory (CVE-2026-84428)\n\nAffected packages:\n\n- `fastify < 5.12.2`\n\nPatched in:\n\n- `fastify 5.12.2`\n\nSource: https://github.com/advisories/GHSA-9q9j-q6p8-xq58","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}