CVE-2026-112362
Full vulnerability record from the local CVENow database.
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.
View original CVE JSON
{
"id": "CVE-2026-112362",
"sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb",
"published": "2026-10-27T12:17:04.970",
"lastModified": "2026-10-27T15:03:41.023",
"vulnStatus": "Awaiting Analysis",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "@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."
}
],
"affected": [
{
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"affectedData": [
{
"vendor": "@fastify/express",
"product": "@fastify/express",
"defaultStatus": "unaffected",
"packageURL": "pkg:npm/@fastify/express",
"versions": [
{
"version": "4.0.5",
"lessThan": "4.0.9",
"versionType": "semver",
"status": "affected"
},
{
"version": "4.0.9",
"versionType": "semver",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {
"cvssMetricV31": [
{
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"type": "Secondary",
"cvssData": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
"baseScore": 9.1,
"baseSeverity": "CRITICAL",
"attackVector": "NETWORK",
"attackComplexity": "LOW",
"privilegesRequired": "NONE",
"userInteraction": "NONE",
"scope": "UNCHANGED",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"availabilityImpact": "NONE"
},
"exploitabilityScore": 3.9,
"impactScore": 5.2
}
]
},
"weaknesses": [
{
"source": "ce714d77-add3-4f53-aff5-83d477b104bb",
"type": "Secondary",
"description": [
{
"lang": "en",
"value": "CWE-436"
}
]
}
],
"references": [
{
"url": "https://cna.openjsf.org/security-advisories.html",
"source": "ce714d77-add3-4f53-aff5-83d477b104bb"
},
{
"url": "https://github.com/fastify/fastify-express/security/advisories/GHSA-6h42-57hq-9746",
"source": "ce714d77-add3-4f53-aff5-83d477b104bb"
}
]
}