{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-84428", "assignerOrgId": "ce714d77-add3-4f53-aff5-83d477b104bb", "state": "PUBLISHED", "assignerShortName": "openjs", "dateReserved": "2026-09-01T18:21:51.906Z", "datePublished": "2026-09-04T10:24:27.809Z", "dateUpdated": "2026-09-04T10:24:27.809Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "ce714d77-add3-4f53-aff5-83d477b104bb", "shortName": "openjs", "dateUpdated": "2026-09-04T10:24:27.809Z"}, "descriptions": [{"lang": "en", "value": "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 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.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "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 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."}]}], "affected": [{"vendor": "fastify", "product": "fastify", "defaultStatus": "unaffected", "versions": [{"versionType": "semver", "status": "affected", "version": "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-9q9j-q6p8-xq58"}, {"url": "https://cna.openjsf.org/security-advisories.html"}], "credits": [{"lang": "en", "type": "reporter", "value": "schecthellraiser606"}, {"lang": "en", "type": "remediation developer", "value": "mcollina"}, {"lang": "en", "type": "remediation developer", "value": "UlisesGascon"}], "title": "fastify vulnerable to header validation bypass via incomplete schema case normalization", "metrics": [{"format": "CVSS", "cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N", "baseScore": 7.5, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-178", "lang": "en", "description": "CWE-178: Improper Handling of Case Sensitivity", "type": "CWE"}]}], "x_generator": {"engine": "cve-kit 1.0.0"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "packageURL": "pkg:npm/fastify", "product": "fastify", "vendor": "fastify", "versions": [{"lessThan": "5.12.2", "status": "affected", "version": "0", "versionType": "semver"}, {"status": "unaffected", "version": "5.12.2", "versionType": "semver"}]}], "source": "ce714d77-add3-4f53-aff5-83d477b104bb"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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 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."}], "id": "CVE-2026-84428", "lastModified": "2026-09-04T11:17:19.317", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "ce714d77-add3-4f53-aff5-83d477b104bb", "type": "Secondary"}]}, "published": "2026-09-04T11:17:19.317", "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-9q9j-q6p8-xq58"}], "sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-178"}], "source": "ce714d77-add3-4f53-aff5-83d477b104bb", "type": "Secondary"}]}

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