{"cve":"CVE-2026-3419","nvd":{"published":"2026-03-06T18:16:22.213","modified":"2026-06-17T10:43:34.207","status":"Analyzed","description":"Fastify incorrectly accepts malformed `Content-Type` headers containing trailing characters after the subtype token, in violation of RFC 9110 §8.3.1(https://httpwg.org/specs/rfc9110.html#field.content-type). For example, a request sent with Content-Type: application/json garbage passes validation and is processed normally, rather than being rejected with 415 Unsupported Media Type.\n\nWhen regex-based content-type parsers are in use (a documented Fastify feature), the malformed value is matched against registered parsers using the full string including the trailing garbage. This means a request with an invalid content-type may be routed to and processed by a parser it should never have reached.\n\nImpact:\nAn attacker can send requests with RFC-invalid Content-Type headers that bypass validity checks, reach content-type parser matching, and be processed by the server. Requests that should be rejected at the validation stage are instead handled as if the content-type were valid.\n\nWorkarounds:\nDeploy a WAF rule to protect against this\n\nFix:\n\nThe fix is available starting with v5.8.1.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","score":5.3},"cwes":["CWE-185"],"references":["https://cna.openjsf.org/security-advisories.html","https://github.com/advisories/GHSA-573f-x89g-hqp9","https://github.com/fastify/fastify/commit/67f6c9b32cb3623d3c9470cc17ed830dd2f083d7","https://github.com/fastify/fastify/security/advisories/GHSA-573f-x89g-hqp9","https://httpwg.org/specs/rfc9110.html#field.content-type"],"products":["fastify:fastify"],"source":"nvd","synced_at":"2026-10-19T22:25:53.701907451+00:00"},"epss":{"cve":"CVE-2026-3419","score":0.00365,"percentile":0.30413,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-573f-x89g-hqp9","url":"https://osv.dev/vulnerability/GHSA-573f-x89g-hqp9","summary":"Fastify's Missing End Anchor in \"subtypeNameReg\" Allows Malformed Content-Types to Pass Validation","modified":"2026-07-08T08:14:43.625968787Z","packages":[{"ecosystem":"npm","name":"fastify","purl":"pkg:npm/fastify","ranges":[">=5.7.2 <5.8.1"],"fixed":["5.8.1"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}