Summary
Nest: Middleware Bypass on Fastify via Trailing Slash
References
Kudos goes to @a-tt-om
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.
The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in @nestjs/[email protected]
Frequently Asked Questions
- What is CVE-2026-54281? CVE-2026-54281 is a high-severity incorrect authorization vulnerability in @nestjs/platform-fastify (npm), affecting versions <= 11.1.23. It is fixed in 11.1.24. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
- Which versions of @nestjs/platform-fastify are affected by CVE-2026-54281? @nestjs/platform-fastify (npm) versions <= 11.1.23 is affected.
- Is there a fix for CVE-2026-54281? Yes. CVE-2026-54281 is fixed in 11.1.24. Upgrade to this version or later.
- Is CVE-2026-54281 exploitable, and should I be worried? Whether CVE-2026-54281 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-54281 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-54281? Upgrade
@nestjs/platform-fastifyto 11.1.24 or later.