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Vulnerability record · CVE-2026-6414 · published 16 April 2026

CVE-2026-6414: Fastify-static vulnerability

Fastify · Fastify Static

@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.

5.9 CVSS 3.1 Medium EPSS 0.45% · top 63.5% CWE-177 · CWE-177
5.9CVSS 3.1 base score
0.45%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

Description

@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.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://cna.openjsf.org/security-advisories.html Third Party Advisory
https://github.com/fastify/fastify-static/security/advisories/GHSA-x428-ghpx-8j92 Vendor Advisory
https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69p Not Applicable
https://github.com/honojs/hono/security/advisories/GHSA-q5qw-h33p-qvwr Not Applicable

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

8.8CVE-2021-22964Fastify-static uncontrolled resource consumption vulnerabilityA redirect vulnerability in the `fastify-static` module version >= 4.2.4 and < 4.4.1 allows remote attackers to redirect Mozilla Firefox users to arb…EPSS 1.0%7.5CVE-2026-18427Fastify-static path traversal vulnerability@fastify/static before version 10.1.3 contains an incomplete fix for a previous route guard bypass. The static file handler rejected only parent dire…EPSS 0.66%7.5CVE-2026-15074Fastify-static path traversal vulnerability@fastify/static up to and including version 10.1.0 fails to reject dot-dot path segments in request pathnames before the file-resolution stage. This …EPSS 0.67%6.1CVE-2021-22963Fastify-static open redirect vulnerabilityA redirect vulnerability in the fastify-static module version < 4.2.4 allows remote attackers to redirect users to arbitrary websites via a double sl…EPSS 1.2%5.3CVE-2026-7120Fastify-static vulnerability@fastify/static evaluates the allowedPath callback before normalizing dot segments and duplicate path separators in the pathname used for file resolu…EPSS 0.37%5.3CVE-2026-6410Fastify-static path traversal vulnerability@fastify/static versions 8.0.0 through 9.1.0 allow path traversal when directory listing is enabled via the list option. The dirList.path() function …EPSS 0.53%

Source: NIST National Vulnerability Database (record CVE-2026-6414), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.