@fastify/static vulnerable to route guard bypass via encoded path separators
### Impact `@fastify/static` v9.1.0 and earlier decodes percent-encoded path separators (`%2F`) before filesystem resolution, but Fastify's router treats them as literal characters. This creates a routing mismatch: route guards on `/admin/*` do not match `/admin%2Fsecret.html`, but @fastify/static decodes it to `/admin/secret.html` and serves the file. Applications that rely on route-based middleware or guards to protect files served by @fastify/static can be bypassed with encoded path separators. ### Patches Upgrade to `@fastify/static` >= 9.1.1. ### Workarounds None. Upgrade to the patched version.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-6414US | — | — | ||
@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. Th… | ||||
references
External citations — patches, advisories, analysis.
- https://cna.openjsf.org/security-advisories.htmlWEB
- https://github.com/fastify/fastify-staticPACKAGE
- https://github.com/fastify/fastify-static/security/advisories/GHSA-x428-ghpx-8j92WEB
- https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69pWEB
- https://github.com/honojs/hono/security/advisories/GHSA-q5qw-h33p-qvwrWEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-6414ADVISORY
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