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GHSA-r4wm-x892-vjmx
No affected components available
Impact
What kind of vulnerability is it? Who is impacted?
A NestJS application using @nestjs/platform-fastify can allow bypass of any middleware when Fastify path-normalization options (e.g., ignoreTrailingSlash, ignoreDuplicateSlashes, useSemicolonDelimiter) are enabled. In affected route-scoped middleware setups, variant paths may skip middleware checks while still reaching the protected handler.
The bug is a path canonicalization mismatch between middleware matching and route matching in Nest’s Fastify adapter.
Nest passes Fastify routerOptions (such as ignoreTrailingSlash, ignoreDuplicateSlashes, useSemicolonDelimiter) to the Fastify router in packages/platform-fastify/adapters/fastify-adapter.ts:253.
But middleware execution is decided by a separate regex check over req.originalUrl in packages/platform-fastify/adapters/fastify-adapter.ts:706 and packages/platform-fastify/adapters/fastify-adapter.ts:713.
If that regex does not match, Nest does next() and skips the middleware (packages/platform-fastify/adapters/fastify-adapter.ts:714), while Fastify may still normalize the same path and route it to the protected handler. So the vulnerability exists because security checks (middleware) and request dispatch(router) use different URL interpretations.
This is a fail-open design issue (inconsistent normalization), not just a bad app config: non-default router options make the mismatch reachable.
Patches
Fixed in @nestjs/platform-fastify@11.1.14
References
Credit goes to Fluidattacks (Cristian Vargas) https://fluidattacks.com/advisories/neton
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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