CVE-2026-33804

@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 duplicat...

@bechara/crux (>=6.0.0 <=6.6.2), @cappa/cli (>=0.1.0 <=0.8.2) +10 more potentially affected by CVE-2026-33804 via @fastify/middie (>=9.0.2 <=9.3.1)

@fastify/middie NPM version =9.0.2, =6.0.0, =0.1.0, =0.1.0, =1.0.0, =1.0.11, =0.1.51, =1.0.36, =11.0.0, =1.3.0, =5.0.0, =0.6.1-dev, =1.1.48 Source cves: CVE-2026-33804 Source advisory: SNYK:JS-FASTIFYMIDDIE-16098212...

CVE-2026-33804 @fastify/middie vulnerable to middleware bypass via deprecated ignoreDuplicateSlashes option

@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 duplicat...