Report: CVE-2026-33804 - @fastify/middie vulnerable to middleware bypass via deprecated ignoreDuplicateSl

Report: CVE-2026-33804 - @fastify/middie vulnerable to middleware bypass via deprecated ignoreDuplicateSl

CVE ID :CVE-2026-33804 Published : April 16, 2026, 1:56 p.m. | 1 hour, 1 minute ago 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. Severity: 7.4 | HIGH Visit the link for more details, such as CVSS details, affected products, timeline, and more...

CVE Details

Severity
HIGH
Published
April 16, 2026