How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

394,002

Total vulnerabilities in the database

@nestjs/platform-fastify: Path-scoped middleware bypass via absolute-form request targets — @nestjs / platform-fastify

Authentication Bypass Using an Alternate Path or Channel

| Field | Value | | --- | --- | | Ecosystem | npm | | Package | @nestjs/platform-fastify | | Affected versions | >= 12.0.0, < 12.0.2 and < 11.2.4 | | Patched versions | 12.0.2 and 11.2.4 (upgrade to 12.0.3 / 11.2.5) |

Summary

On the Fastify adapter, an HTTP request that uses an absolute-form request target (GET http://host/path HTTP/1.1 instead of GET /path HTTP/1.1) reaches the route handler without running the path-scoped Nest middleware bound to that route. Applications that enforce authentication or authorization in middleware execute the protected handler with those checks skipped.

Impact

Any application that

uses @nestjs/platform-fastify, and
binds middleware to specific paths via MiddlewareConsumer.forRoutes(...) or .exclude(...), and
is reachable by a client that controls the raw request line.

Node's HTTP server accepts absolute-form targets, so no special server configuration is needed. Exposure is reduced when a reverse proxy in front of the application rewrites the request target to origin-form, which most do.

Where the bypassed middleware performs authentication or authorization, the result is an authentication or authorization bypass. Where it performs logging, rate limiting or body handling, those are silently skipped instead.

Details

Fastify's router (find-my-way) resolves an absolute-form target to its path before matching, so the route handler is dispatched normally. Two places on the middleware side matched against the raw request target instead:

The bundled copy of the @fastify/middie engine at packages/platform-fastify/adapters/middie/fastify-middie.ts. NestJS carried this fork to apply an earlier path-decoding fix and it did not track the upstream absolute-form fix released in @fastify/[email protected].
FastifyAdapter's own re-check in createMiddlewareFactory(), which tests the middleware path regexp against req.originalUrl.

Both normalized and percent-decoded the target, but neither resolved absolute-form to a path, so the router and the middleware layer disagreed about which path was being requested.

A second, related defect contributed. Because the adapter always passes routerOptions (to install the version constraint), Fastify did not reflect the deprecated top-level router options (ignoreTrailingSlash, ignoreDuplicateSlashes, caseSensitive, useSemicolonDelimiter) in initialConfig.routerOptions, which is what the middleware engine reads. Applications passing those options at the top level had middleware normalize paths differently from the router, which widened the mismatch.

Proof of concept

@Controller(&#039;users&#039;)
export class UsersController {
  @Get()
  findAll() {
    return &#039;protected data&#039;;
  }
}

@Module({ controllers: [UsersController] })
export class AppModule implements NestModule {
  configure(consumer: MiddlewareConsumer) {
    consumer
      .apply((req, res) =&gt; res.end(&#039;blocked by auth middleware&#039;))
      .forRoutes({ path: &#039;users&#039;, method: RequestMethod.GET });
  }
}

supertest and light-my-request always emit origin-form targets, so the request has to be written to the socket:

const { connect } = require(&#039;node:net&#039;);

const socket = connect(3000, &#039;127.0.0.1&#039;, () =&gt; {
  socket.write(
    &#039;GET http://127.0.0.1:3000/users HTTP/1.1\r\n&#039; +
      &#039;Host: 127.0.0.1:3000\r\n&#039; +
      &#039;Connection: close\r\n\r\n&#039;,
  );
});
socket.pipe(process.stdout);

Observed on an affected version: protected data — the middleware did not run. Expected, and observed on a patched version: blocked by auth middleware.

Patches

Fixed in 12.0.2 and 11.2.4. Upgrading to 12.0.3 or 11.2.5 is recommended.

The bundled @fastify/middie fork was removed and the package now depends on @fastify/[email protected], which resolves absolute-form targets before matching.
The adapter resolves absolute-form targets in its own route check, mirroring find-my-way.
Deprecated top-level Fastify router options are folded into routerOptions so the middleware engine and the router normalize paths identically.

Workarounds

If you cannot upgrade, reject non-origin-form request targets before middleware runs. Register the hook on the Fastify instance before the application is initialized, so that it runs ahead of the middleware engine's own onRequest hook, and confirm with the request above that the rejection takes effect:

const adapter = new FastifyAdapter();
adapter.getInstance().addHook(&#039;onRequest&#039;, (request, reply, done) =&gt; {
  const target = request.raw.url ?? &#039;&#039;;
  // &quot;*&quot; is the legitimate request target of &quot;OPTIONS * HTTP/1.1&quot;
  if (target[0] !== &#039;/&#039; &amp;&amp; target !== &#039;*&#039;) {
    reply.code(400).send();
    return;
  }
  done();
});

Rejecting or normalizing absolute-form targets at a reverse proxy in front of the application is equally effective.

Credit

Reported by ZeroVuln Labs.

Published: Sep 30, 2026
Updated: Oct 2, 2026
GHSA: GHSA-9c5c-9qcx-q35q
Severity: High
Exploit:
CISA KEV:

CVSS v3:

Severity: High
Score: 7.4
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

CWEs:

Affected Software
References

Software	Affected versions
@nestjs / platform-fastify	`< 11.2.4`
@nestjs / platform-fastify	`>= 12.0.0, < 12.0.2`

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.