@fastify/middie is the Express-style middleware engine for Fastify. In versions from 9.0.0 through 9.3.5, the use() function joined a path-scoped middleware's mount path to the plugin scope prefix in a way that could diverge from the path Fastify's router serves, most often when...
Vendor
@fastify/middie vulnerabilities
7 published CVES affecting @fastify/middie, from public sources (CVE.org, NVD, CISA KEV, FIRST EPSS, OSV).
- Total
- 7
- Critical
- 5
- High
- 2
- Medium
- 0
- Low
- 0
- Unscored
- 0
- CISA KEV
- 0
Products
Latest @fastify/middie CVEs
Newest publication first
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CriticalCVSS 9.1 EPSS 0.31%
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CriticalCVSS 9.1 EPSS 0.52%
@fastify/middie versions >= 9.1.0 and before 9.3.4 decide whether to run path-scoped middleware by matching against the raw request target, while the Fastify router resolves an absolute-form request target to its path before dispatching. Because the two layers evaluate different...
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HighCVSS 7.5 EPSS 0.50%
@fastify/middie versions 9.1.0 through 9.3.2 fail to guard the URL normalization step used by the standalone engine when incoming request paths contain malformed percent-encoded sequences. Inputs such as an incomplete percent escape or a truncated multibyte sequence cause the und...
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CriticalCVSS 9.1 EPSS 0.52%
@fastify/middie versions 9.1.0 through 9.3.2 decode the encoded slash %2F inside path parameter values before matching middleware paths, while Fastify's underlying router preserves the encoding during route lookup. The two layers disagree on the canonical request path, so the mid...
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CriticalCVSS 9.1 EPSS 0.28%
@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 reque...
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CVE-2026-6270 @fastify/middie vulnerable to middleware authentication bypass in child plugin scopes
PublishedCriticalCVSS 9.1 EPSS 0.50%@fastify/middie versions 9.3.1 and earlier do not register inherited middleware directly on child plugin engine instances. When a Fastify application registers authentication middleware in a parent scope and then registers child plugins with @fastify/middie, the child scope does...
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HighCVSS 8.2 EPSS 0.43%
A vulnerability in @fastify/middie versions < 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)). When Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDeli...
Sources: CVE.org, NVD, CISA KEV, FIRST EPSS, OSV and public exploit-reference metadata. Product matching comes from the published CVE records. A proof-of-concept means public code exists; it is not evidence of exploitation.