🛡️ CVE-2026-33808
🔴 CVSS 9.5 — Critical ✅ No Known Exploit CWE-436 NVD
9.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Impact@fastify/express v4.0.4 and earlier fails to normalize URLs before passing them to Express middleware when Fastify router normalization options are enabled. This allows complete bypass of path-scoped authentication middleware via duplicate slashes when ignoreDuplicateSlashes is enabled, or via semicolon delimiters when useSemicolonDelimiter is enabled. In both cases, Fastify router normalizes the URL and matches the route, but @fastify/express passes the original un-normalized URL to Express middleware, which fails to match and is skipped. An unauthenticated attacker can access protected routes by manipulating the URL path. PatchesUpgrade to @fastify/express v4.0.5 or later.

Details

Severity CRITICAL
CVSS Score 9.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CWE CWE-436
Public Exploit ✅ No
Source NVD
Published 2026-04-16
Updated 2026-06-10
Modified 2026-06-09
Fix URL N/A

Affected Packages

Software From version Fixed in
@fastify/express — —
fastify\/express — 4.0.5
unknown — —

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