Vulnerability in Fastify Fastify-Static
CVE-2026-6414
@fastify/static versions 8.0.0 through 9.1.0 decode percent-encoded path separators (%2F) before filesystem resolution, while Fastify's router treats them as literal characters. This mismatch allows attackers to bypass route-based middleware or guards that protect files served by @fastify/static. For example, a route guard on a protected path can be circumvented by encoding the path separator in the URL. Upgrade to @fastify/static 9.1.1 to fix this issue. There are no workarounds.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.004 (37.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 38th percentile — 37.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000
Affected products
- Fastify Fastify-Static
- @Fastify/static — versions 8.0.0, 9.1.1
Weakness classification (CWE)
References
- ce714d77-add3-4f53-aff5-83d477b104bb (Not Applicable)
- ce714d77-add3-4f53-aff5-83d477b104bb (Not Applicable)
- ce714d77-add3-4f53-aff5-83d477b104bb (Vendor Advisory)
- ce714d77-add3-4f53-aff5-83d477b104bb (Third Party Advisory)
Frequently asked questions
- What is CVE-2026-6414?
- CVE-2026-6414 is a medium-severity vulnerability in Fastify Fastify-Static, classified under CWE-177. CVSS score: 5.9/10. Published 2026-04-16.
- How severe is CVE-2026-6414?
- Medium severity. CVSS v3 base score is 5.9 out of 10.