CVE-2026-54281
Impact
An authentication bypass vulnerability exists in @nestjs/platform-fastify (confirmed on version 11.1.24, the latest available release at time of report). When middleware is registered through NestJS's MiddlewareConsumer.forRoutes() API on the Fastify adapter, an unauthenticated client can bypass the Nest middleware registered for that route by simply appending a trailing slash (/) to the request URL.
This bypass works on the default Fastify adapter configuration — no special router options need to be enabled. Applications using the standard CRUD route shape (GET /resource and GET /resource/:id) are affected when they protect those routes with MiddlewareConsumer.forRoutes() middleware.
Patches
Fixed in @nestjs/platform-fastify@11.1.24
References
Kudos goes to @a-tt-om
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Exploitation outlook
- Low exploitation risk0.50% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 40% of all EPSS-scored CVEs.
Advisory coverage (1)
- highGHSA-6v32-fjc9-9qf6: Nest: Middleware Bypass on Fastify via Trailing Slashghsa · 2026-06-15
External references
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[](https://www.csirts.com/cve/CVE-2026-54281)