CVE-2026-33804
7.4 · HIGHOverview
CVE-2026-33804 is a high-severity vulnerability affecting fastify fastify\/middie. It was published on April 16, 2026 and has a CVSS 3.1 base score of 7.4 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.4, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
@fastify/middie versions 9.3.1 and earlier are vulnerable to middleware bypass when the deprecated Fastify ignoreDuplicateSlashes option is enabled. The middleware path matching logic does not account for duplicate slash normalization performed by Fastify's router, allowing requests with duplicate slashes to bypass middleware authentication and authorization checks. This only affects applications using the deprecated ignoreDuplicateSlashes option. Upgrade to @fastify/middie 9.3.2 to fix this issue. There are no workarounds other than disabling the ignoreDuplicateSlashes option.
Remediation
Check the references section for vendor advisories and patches from fastify. Update fastify\/middie to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| fastify | fastify\/middie | >= 0, < 9.3.2 | Affected |
Frequently Asked Questions
What is CVE-2026-33804?
CVE-2026-33804 is a high-severity vulnerability affecting fastify fastify\/middie. It was published on April 16, 2026 and has a CVSS 3.1 base score of 7.4 (HIGH).
How severe is CVE-2026-33804?
This vulnerability has a CVSS 3.1 base score of 7.4, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-33804?
Check the references section for vendor advisories and patches from fastify. Update fastify\/middie to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-33804?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-33804 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
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