What is CVE-2026-3419?

CVE-2026-3419 is a medium-severity vulnerability in Fastify, classified under Incorrect Regular Expression. CVSS score: 5.3/10. Published 2026-03-06.

How severe is CVE-2026-3419?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Fastify

CVE-2026-3419

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 wit…

EPSS: 0.000 (4.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

Affected products

Fastify — versions 5.7.2, 5.8.1

Weakness classification (CWE)

CWE-185 — Incorrect Regular Expression

References

github.com/fastify/fastify/security/advisories/GHSA-573f-x89g-hqp9
github.com/fastify/fastify/commit/67f6c9b32cb3623d3c9470cc17ed830dd2f083d7
httpwg.org/specs/rfc9110.html
github.com/advisories/GHSA-573f-x89g-hqp9
cna.openjsf.org/security-advisories.html
www.cve.org/CVERecord

Frequently asked questions

What is CVE-2026-3419?: CVE-2026-3419 is a medium-severity vulnerability in Fastify, classified under Incorrect Regular Expression. CVSS score: 5.3/10. Published 2026-03-06.
How severe is CVE-2026-3419?: Medium severity. CVSS v3 base score is 5.3 out of 10.