Medium [CVE-2026-18504] Schema validation bypass via root primitive coercion mismatch
This medium-severity Red Hat Linux advisory covers CVE-2026-18504 affecting Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat OpenShift AI (RHOAI), Red Hat OpenShift Dev Spaces.
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Summary
fastify is a fast and low overhead web framework for Node.js. Versions of fastify before 5.12.1 are affected by a schema validation bypass when a request body schema targets a root primitive value.
As a result, a request that should have failed validation can reach application logic with a value that does not satisfy the schema, which can undermine integrity and access-control checks that rely on the validated type. Users should upgrade to fastify 5.12.1, which fixes the mismatch.
No known workarounds are available. A flaw was found in fastify.
This occurs because the validation process may coerce a JSON string into an expected type, but the original unvalidated string is then passed to the application logic. Red Hat severity: Moderate — CVSS 5.4 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N).
Weakness: CWE-843. Affected Red Hat products: Red Hat Enterprise Linux AI (RHEL AI) 3; Red Hat OpenShift AI (RHOAI); Red Hat OpenShift Dev Spaces.
Red Hat does not currently list a fixing RHSA for this CVE.
- < 5.12.1
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Mitigation
The vendor states no workaround or mitigation is currently available. Prioritize upgrading to a fixed release, and follow the official advisory for interim guidance.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
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