CVEvulnerability
CVE-2026-33808
9.1 CRITICAL
Official page ↗
- Status
- Analyzed
- Published
- 2026-04-15
- Last modified
- 2026-10-26
- Assigner
- ce714d77-add3-4f53-aff5-83d477b104bb
- CVSS 4.0 (ce714d77-add3-4f53-aff5-83d477b104bb)
- 9.1 CRITICAL — CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- CVSS 3.1 ([email protected])
- 9.1 CRITICAL — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- Weaknesses
- CWE-436
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.
Affected configurations
• fastify fastify\/express (< 4.0.5)
Related
Weakness · CWE (1)
- CWE-436 Interpretation Conflict weakness
References
- https://cna.openjsf.org/security-advisories.html Vendor Advisory
- https://github.com/fastify/fastify-express/security/advisories/GHSA-6hw5-45gm-fj88 Exploit, Mitigation, Vendor Advisory
- https://github.com/fastify/fastify-express/security/advisories/GHSA-6hw5-45gm-fj88 Exploit, Mitigation, Vendor Advisory