@fastify/static vulnerable to route guard bypass via encoded path separators

MITRE NVD CVE.ORG JSON API Print: PDF PDF

Summary

CVECVE-2026-6414
StatePUBLISHED
Assigneropenjs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-16 13:16:52 UTC
Updated2026-04-17 15:17:00 UTC
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.

Risk And Classification

Primary CVSS: v3.1 5.9 MEDIUM from ce714d77-add3-4f53-aff5-83d477b104bb

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

EPSS: 0.000110000 probability, percentile 0.011830000 (date 2026-04-20)

Problem Types: CWE-177 | CWE-177 CWE-177: Improper Handling of URL Encoding (Hex Encoding)

VersionSourceTypeScoreSeverityVector
3.1ce714d77-add3-4f53-aff5-83d477b104bbSecondary5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
3.1CNACVSS5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA @fastifystatic @fastify/static affected 8.0.0 9.1.1 semver Not specified
CNA @fastifystatic @fastify/static unaffected 9.1.1 semver Not specified

References

ReferenceSourceLinkTags
cna.openjsf.org/security-advisories.html ce714d77-add3-4f53-aff5-83d477b104bb cna.openjsf.org
github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69p ce714d77-add3-4f53-aff5-83d477b104bb github.com
github.com/honojs/hono/security/advisories/GHSA-q5qw-h33p-qvwr ce714d77-add3-4f53-aff5-83d477b104bb github.com
github.com/fastify/fastify-static/security/advisories/GHSA-x428-ghpx-8j92 ce714d77-add3-4f53-aff5-83d477b104bb github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: blakeembrey (en)

CNA: mcollina (en)

CNA: UlisesGascon (en)

CNA: climba03003 (en)

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