What is CVE-2026-22037?

CVE-2026-22037 is a high-severity vulnerability in Fastify Fastify-express, classified under CWE-177. CVSS score: 8.4/10. Published 2026-01-19.

How severe is CVE-2026-22037?

High severity. CVSS v3 base score is 8.4 out of 10.

Vulnerability in Fastify Fastify-express

CVE-2026-22037

The @fastify/express plugin adds full Express compatibility to Fastify. A security vulnerability exists in @fastify/express prior to version 4.0.3 where middleware registered with a specific path prefix can be bypassed using URL-encoded ch…

EPSS: 0.000 (10.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L.

Affected products

Fastify Fastify-express — versions < 4.0.3

Weakness classification (CWE)

References

https://github.com/fastify/fastify-express/security/advisories/GHSA-g6q3-96cp-5r5m (x_refsource_CONFIRM)
https://github.com/fastify/fastify-express/commit/dc02a3fe1387f945143f22597baa42557d549a40 (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-22037?: CVE-2026-22037 is a high-severity vulnerability in Fastify Fastify-express, classified under CWE-177. CVSS score: 8.4/10. Published 2026-01-19.
How severe is CVE-2026-22037?: High severity. CVSS v3 base score is 8.4 out of 10.