Summary
Nest has a Fastify URL Encoding Middleware Bypass (TOCTOU)
A NestJS application is vulnerable if it meets all of the following criteria:
- Platform: Uses
@nestjs/platform-fastify. - Security Mechanism: Relies on
NestMiddleware(viaMiddlewareConsumer) for security checks (authentication, authorization, etc.), or throughapp.use() - Routing: Applies middleware to specific routes using string paths or controllers (e.g.,
.forRoutes('admin')).
Example Vulnerable Config:
// app.module.ts
export class AppModule implements NestModule {
configure(consumer: MiddlewareConsumer) {
consumer
.apply(AuthMiddleware) // Security check
.forRoutes('admin'); // Vulnerable: Path-based restriction
}
}
Attack Vector:
- Target Route:
/admin - Middleware Path:
admin - Attack Request:
GET /%61dmin - Result: Middleware is skipped (no match on
%61dmin), but controller for/adminis executed.
Consequences:
- Authentication Bypass: Unauthenticated users can access protected routes.
- Authorization Bypass: Restricted administrative endpoints become accessible to lower-privileged users.
- Input Validation Bypass: Middleware performing sanitization or validation can be skipped.
Resources
Credit goes to Hacktron AI for reporting this issue.
Impact
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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Patched in @nestjs/[email protected]
Frequently Asked Questions
- What is CVE-2025-69211? CVE-2025-69211 is a medium-severity security vulnerability in @nestjs/platform-fastify (npm), affecting versions < 11.1.10. It is fixed in 11.1.11.
- Which versions of @nestjs/platform-fastify are affected by CVE-2025-69211? @nestjs/platform-fastify (npm) versions < 11.1.10 is affected.
- Is there a fix for CVE-2025-69211? Yes. CVE-2025-69211 is fixed in 11.1.11. Upgrade to this version or later.
- Is CVE-2025-69211 exploitable, and should I be worried? Whether CVE-2025-69211 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-2025-69211 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-2025-69211? Upgrade
@nestjs/platform-fastifyto 11.1.11 or later.