Vulnerability Details 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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 2.8%
CVSS Severity
CVSS v3 Score 5.9
References
Products affected by CVE-2026-6414
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cpe:2.3:a:fastify:fastify-static:8.0.0
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cpe:2.3:a:fastify:fastify-static:8.0.1
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cpe:2.3:a:fastify:fastify-static:8.0.2
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cpe:2.3:a:fastify:fastify-static:8.0.3
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cpe:2.3:a:fastify:fastify-static:8.0.4
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cpe:2.3:a:fastify:fastify-static:8.1.0
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cpe:2.3:a:fastify:fastify-static:8.1.1
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cpe:2.3:a:fastify:fastify-static:8.2.0
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cpe:2.3:a:fastify:fastify-static:8.3.0
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cpe:2.3:a:fastify:fastify-static:9.0.0
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cpe:2.3:a:fastify:fastify-static:9.1.0