CVE-2026-6414

Summary

@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.

Affected Software

VendorProductVersion RangeStatus
@fastify/static@fastify/static8.0.0 < 9.1.1affected
@fastify/static@fastify/static9.1.1unaffected

Weaknesses

  • CWE-177: CWE-177: Improper Handling of URL Encoding (Hex Encoding)

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References