GHSA-gjxx-92w9-8v8f Clerk: SSRF in the opt-in clerkFrontendApiProxy feature may leak secret keys to unintended host

• npm @clerk/backend: >= 3.0.0, < 3.2.3 → fixed in 3.2.3 • npm @clerk/express: >= 2.0.0, < 2.0.7 → fixed in 2.0.7 • npm @clerk/hono: >= 0.1.0, < 0.1.5 → fixed in 0.1.5 • npm @clerk/fastify: >= 3.1.0, < 3.1.5 → fixed in 3.1.5

Summary The `clerkFrontendApiProxy` function in `@clerk/backend` is vulnerable to Server-Side Request Forgery (SSRF). An unauthenticated attacker can craft a request path that causes the proxy to send the application's `Clerk-Secret-Key` to an attacker-controlled server. Affected packages Only applications that have opted into the `frontendApiProxy` feature are affected. This feature is not enabled by default. Users of `@clerk/nextjs` are not affected due to how the framework handles repeated `/` in request paths. | Package | Affected versions | Fixed version | |---|---|---| | `@clerk/backend` | `>= 3.0.0, = 2.0.0, = 0.1.0, = 3.1.0, <= 3.1.4` | `3.1.5` | Search your codebase for the `frontendApiProxy` option. If none of the patterns below appear in your code, you are not affected. @clerk/express ```ts app.use(clerkMiddleware({ frontendApiProxy: { enabled: true } })); ``` @clerk/hono ```ts app.use('*', clerkMiddleware({ frontendApiProxy: { enabled: true } })); ``` @clerk/fastify ```ts fastify.register(clerkPlugin, { frontendApiProxy: { enabled: true } }); ``` @clerk/backend ```ts import { clerkFrontendApiProxy } from '@clerk/backend/proxy'; ``` A quick way to check across your entire project: ```sh grep -r "frontendApiProxy\|clerkFrontendApiProxy" . ``` If there are no matches, you are not using this feature. Recommended actions Clerk's internal logs show no evidence of users utilizing the built-in proxy with the impacted versions. Despite that, if you are on an impacted version and use the built-in proxy we recommend upgrading and rotating your Clerk Secret Key immediately. 1. Upgrade to the patched version of `@clerk/backend` (and `@clerk/express`, `@clerk/hono`, etc.) 2. Rotate your Clerk Secret Key after upgrading - if an attacker exploited this vulnerability, they may have captured your key. Rotate it in the Clerk Dashboard under API Keys. You should deploy your application with the updated key before revoking the existing key. 3. Audit access logs for requests to your proxy endpoint (`/__clerk/` by default) containing double slashes in the path. Credit Discovered during an internal code audit.