CVE-2026-6414
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · unedited@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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe @fastify/static package decodes percent-encoded path separators (%2F) before filesystem resolution, while Fastify's router treats them as literal characters. This discrepancy allows attackers to bypass route-based middleware or guards that protect files by encoding path separators in the URL, effectively circumventing access controls.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 8.0.0, < 9.1.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check @fastify/static versionRun `npm list @fastify/static` or inspect your package.json and package-lock.json to find the installed version numberAffected if Version is 8.0.0 or higher but below 9.1.1
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Verify @fastify/static is in useSearch your Fastify application source code for `require('@fastify/static')` or `import from '@fastify/static'` to confirm the package is registered, such as `fastify.register(require('@fastify/static'), options)`Affected if Your application registers and uses @fastify/static to serve static files
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Identify static file routes with access controlsReview your route definitions and look for static file serving routes (usually serving from a `root` directory) that have preHandler hooks, authentication middleware, or guard functions appliedAffected if Protected static routes exist that could potentially be bypassed by encoding path separators in the URL
You are affected if @fastify/static version 8.0.0 through 9.1.0 is installed, your application uses it to serve static files, and those files are protected by route-based access controls that could be circumvented using %2F in the URL path.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped9.1.1
Upgrade @fastify/static to version 9.1.1 or later. There are no available workarounds for this vulnerability.
@fastify/[email protected]
- Run `npm install @fastify/[email protected]` or update the dependency in package.json to version 9.1.1 and run `npm install`
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation1.0 h
- Implementation1.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,616.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-6414 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-6414 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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