CVE-2026-33807

CRITICAL EPSS 34.4%
Published Apr 15, 20262mo ago · Modified Jun 17, 20261w ago
9.1 CVSS 3.1
Critical
Find Similar
Published Apr 15, 2026 2mo ago
Last Modified Jun 17, 2026 1w ago

Description

@fastify/express v4.0.4 and earlier contains a path handling bug in the onRegister function that causes middleware paths to be doubled when inherited by child plugins. When a child plugin is registered with a prefix that matches a middleware path, the middleware path is prefixed a second time, causing it to never match incoming requests. This results in complete bypass of Express middleware security controls, including authentication, authorization, and rate limiting, for all routes defined within affected child plugin scopes. No special configuration or request crafting is required. Upgrade to @fastify/express v4.0.5 or later.

CVSS Details

Base Score
9.1
Exploitability
3.9
Impact
5.2
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality High
Integrity High
Availability None

Threat Intelligence

EPSS Exploit Probability
34.4% percentile
Exploit & Patch Status
Public Exploit Known
No Patch Available

Weaknesses 1

CWE-436

Affected Products 1

VendorProductVersionRange
fastifyfastify\/express* <4.0.5

References 2

  • cna.openjsf.org https://cna.openjsf.org/security-advisories.html
    Vendor Advisory
  • github.com https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c
    ExploitMitigationVendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.