{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-76169", "assignerOrgId": "ce714d77-add3-4f53-aff5-83d477b104bb", "state": "PUBLISHED", "assignerShortName": "openjs", "dateReserved": "2026-08-19T09:33:54.670Z", "datePublished": "2026-09-04T09:51:03.556Z", "dateUpdated": "2026-09-04T09:51:03.556Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "ce714d77-add3-4f53-aff5-83d477b104bb", "shortName": "openjs", "dateUpdated": "2026-09-04T09:51:03.556Z"}, "descriptions": [{"lang": "en", "value": "fastify versions >= 4.0.0 and before 5.12.2 can route a malformed URL sent under one plugin prefix to the custom not-found handler of a different sibling plugin, and invoke it without the preHandler hook declared for that handler. The internal not-found router for encapsulated handlers dispatches malformed paths through a single shared handler pointer before URL decoding, ignoring the prefix and skipping the selected handler's normal lifecycle. An unauthenticated attacker can therefore reach an authentication-protected private fallback through an unrelated public prefix and read its full response, bypassing the authentication hook and breaking prefix encapsulation. Users should upgrade to fastify 5.12.2 or later.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "fastify versions >= 4.0.0 and before 5.12.2 can route a malformed URL sent under one plugin prefix to the custom not-found handler of a different sibling plugin, and invoke it without the preHandler hook declared for that handler. The internal not-found router for encapsulated handlers dispatches malformed paths through a single shared handler pointer before URL decoding, ignoring the prefix and skipping the selected handler's normal lifecycle. An unauthenticated attacker can therefore reach an authentication-protected private fallback through an unrelated public prefix and read its full response, bypassing the authentication hook and breaking prefix encapsulation. Users should upgrade to fastify 5.12.2 or later."}]}], "affected": [{"vendor": "fastify", "product": "fastify", "defaultStatus": "unaffected", "versions": [{"versionType": "semver", "status": "affected", "version": "4.0.0", "lessThan": "5.12.2"}, {"versionType": "semver", "status": "unaffected", "version": "5.12.2"}], "packageURL": "pkg:npm/fastify"}], "references": [{"url": "https://github.com/fastify/fastify/security/advisories/GHSA-p68q-wchp-6fh7"}, {"url": "https://cna.openjsf.org/security-advisories.html"}], "credits": [{"lang": "en", "type": "reporter", "value": "vvvvvvvvvvitel"}, {"lang": "en", "type": "remediation developer", "value": "mcollina"}, {"lang": "en", "type": "remediation reviewer", "value": "UlisesGascon"}, {"lang": "en", "type": "finder", "value": "schecthellraiser606"}, {"lang": "en", "type": "finder", "value": "B1gN0Se"}], "title": "fastify vulnerable to authentication bypass via malformed URLs reaching encapsulated not-found handlers", "metrics": [{"format": "CVSS", "cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "baseScore": 7.5, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-288", "lang": "en", "description": "CWE-288: Authentication Bypass Using an Alternate Path or Channel", "type": "CWE"}]}], "x_generator": {"engine": "cve-kit 1.0.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "packageURL": "pkg:npm/fastify", "product": "fastify", "vendor": "fastify", "versions": [{"lessThan": "5.12.2", "status": "affected", "version": "4.0.0", "versionType": "semver"}, {"status": "unaffected", "version": "5.12.2", "versionType": "semver"}]}], "source": "ce714d77-add3-4f53-aff5-83d477b104bb"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "fastify versions >= 4.0.0 and before 5.12.2 can route a malformed URL sent under one plugin prefix to the custom not-found handler of a different sibling plugin, and invoke it without the preHandler hook declared for that handler. The internal not-found router for encapsulated handlers dispatches malformed paths through a single shared handler pointer before URL decoding, ignoring the prefix and skipping the selected handler's normal lifecycle. An unauthenticated attacker can therefore reach an authentication-protected private fallback through an unrelated public prefix and read its full response, bypassing the authentication hook and breaking prefix encapsulation. Users should upgrade to fastify 5.12.2 or later."}], "id": "CVE-2026-76169", "lastModified": "2026-09-04T10:17:12.020", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "ce714d77-add3-4f53-aff5-83d477b104bb", "type": "Secondary"}]}, "published": "2026-09-04T10:17:12.020", "references": [{"source": "ce714d77-add3-4f53-aff5-83d477b104bb", "url": "https://cna.openjsf.org/security-advisories.html"}, {"source": "ce714d77-add3-4f53-aff5-83d477b104bb", "url": "https://github.com/fastify/fastify/security/advisories/GHSA-p68q-wchp-6fh7"}], "sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-288"}], "source": "ce714d77-add3-4f53-aff5-83d477b104bb", "type": "Secondary"}]}

{}

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