CVE-2026-22037: @fastify/express vulnerable to Improper Handling of URL Encoding (Hex Encoding)
fastify · fastify-express
Affected: fastify-express · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 28% of scored CVEs
DescriptionCVE.org
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 characters (e.g., `/%61dmin` instead of `/admin`). While the middleware engine fails to match the encoded path and skips execution, the underlying Fastify router correctly decodes the path and matches the route handler, allowing attackers to access protected endpoints without the middleware constraints. The vulnerability is caused by how @fastify/express matches requests against registered middleware paths. This vulnerability is similar to, but differs from, CVE-2026-22031 because this is a different npm module with its own code. Version 4.0.3 of @fastify/express contains a patch fort the issue.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- fastify · fastify-express< 4.0.3
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- fastify
- Published
- January 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-22037 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.