CVE-2026-2880
Critical
Description
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, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.
SeverityCritical
CVSS9.1
Exploit probability—
Product
@fastify/middie
PublishedFeb 27, 2026
First seenFeb 27, 2026
Weakness typeCWE-20Improper input validation
How to fix
Update
- @fastify/middie9.2.0 or later
- fastify fastify\/middie9.2.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| @fastify/middienpm | v < 9.2.0 | 9.2.0 |
| fastify fastify\/middie | v < 9.2.0 | 9.2.0 |
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