GHSA-573f-x89g-hqp9 · Severity: medium · Ecosystem: npm — Fastify's Missing End Anchor in "subtypeNameReg" Allows Malformed Content-Types to Pass Validation
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. When 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. Impact: An 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. Workarounds: Deploy a WAF rule to protect against this Fix: The fix is available starting with v5.8.1.
Conclusion & alert: CVE-2026-3419 is rated Low Risk (24.6/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.03%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-03-07 | — | 0.03% | — |
Full EPSS history (1 record total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 5.3 | 3.1 | MEDIUM |
|
3.9 | 1.4 | ce714d77-add3-4f53-aff5-83d477b104bb |
GHSA-573f-x89g-hqp9 · Severity: medium · Ecosystem: npm — Fastify's Missing End Anchor in "subtypeNameReg" Allows Malformed Content-Types to Pass Validation
| vendor | priority | summary | link |
|---|---|---|---|
redhat
|
medium | — | https://access.redhat.com/security/cve/CVE-2026-3419 |
| URL | Tags |
|---|---|
| https://cna.openjsf.org/security-advisories.html | Vendor Advisory |
| https://github.com/advisories/GHSA-573f-x89g-hqp9 | Patch Vendor Advisory |
| https://github.com/fastify/fastify/commit/67f6c9b32cb3623d3c9470cc17ed830dd2f083d7 | Patch |
| https://github.com/fastify/fastify/security/advisories/GHSA-573f-x89g-hqp9 | Vendor Advisory |
| https://httpwg.org/specs/rfc9110.html#field.content-type | Technical Description |
| https://www.cve.org/CVERecord?id=CVE-2026-3419 | VDB Entry |