{"id":"CVE-2026-112362","aliases":[],"title":"@fastify/express vulnerable to path-scoped middleware bypass via absolute-form request targets","titleSource":"openjs","descriptionSource":"openjs","products":[{"vendor":"@fastify/express","name":"@fastify/express","platforms":[],"versions":[{"version":"4.0.5","status":"affected","lessThan":"4.0.9","versionType":"semver"},{"version":"4.0.9","status":"unaffected","versionType":"semver"}],"defaultStatus":"unaffected","source":"openjs","url":"https://www.cve.org/CVERecord?id=CVE-2026-112362"}],"remediation":[],"description":"@fastify/express is a Fastify plugin that runs Express middleware inside Fastify. In versions 4.0.5 through 4.0.8, when Fastify runs with the non-default ignoreDuplicateSlashes option enabled, the plugin matches path-scoped Express middleware against a URL whose duplicate-slash normalization has also collapsed the separator after an absolute-form request target's scheme, so Fastify's router resolves the request to the scoped path and runs the handler while the Express layer no longer sees that path. As a result, a request using an absolute-form target can reach a handler on a scoped route such as an admin path while the middleware for authentication, authorization, or rate limiting is skipped. An unauthenticated attacker needs only the non-default ignoreDuplicateSlashes option to be enabled. The issue is fixed in @fastify/express 4.0.9, and users should upgrade to 4.0.9 or later. As a workaround, enforce authentication in a Fastify hook such as preHandler that runs after the router resolves the request, or leave ignoreDuplicateSlashes at its default.","severity":"critical","score":9.1,"published":"2026-10-27T11:27:59.364Z","modified":"2026-10-27T11:27:59.364Z","withdrawn":false,"knownExploited":false,"affected":[],"references":["https://github.com/fastify/fastify-express/security/advisories/GHSA-6h42-57hq-9746","https://cna.openjsf.org/security-advisories.html"],"sources":[{"name":"CVE","id":"CVE-2026-112362","modified":"2026-10-27T11:27:59.364Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-112362"}],"assessments":[{"source":"openjs","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","score":9.1}],"sourceAffected":[],"kev":{"status":"not-listed","checkedAt":"2026-10-28T15:40:31.878Z"},"coverage":[{"source":"NVD","status":"not-checked"},{"source":"GHSA","status":"not-checked"},{"source":"EUVD","status":"not-checked"},{"source":"EPSS","status":"not-checked"}],"evidence":[]}