{"id":"CVE-2026-34076","aliases":["GHSA-gjxx-92w9-8v8f"],"url":"https://o3.security/vulnerability/CVE-2026-34076","summary":"Clerk JavaScript: SSRF in the opt-in clerkFrontendApiProxy feature may leak secret keys to unintended host","details":"## Summary\n\nThe `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.\n\n## Affected packages\n\nOnly 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.\n\n| Package | Affected versions | Fixed version |\n|---|---|---|\n| `@clerk/backend` | `>= 3.0.0, <= 3.2.2` | `3.2.3` |\n| `@clerk/express` | `>= 2.0.0, <= 2.0.6` | `2.0.7` |\n| `@clerk/hono` | `>= 0.1.0, <= 0.1.4` | `0.1.5` |\n| `@clerk/fastify` | `>= 3.1.0, <= 3.1.4` | `3.1.5` |\n\nSearch your codebase for the `frontendApiProxy` option. If none of the patterns below appear in your code, you are not affected.\n\n**@clerk/express**\n```ts\napp.use(clerkMiddleware({ frontendApiProxy: { enabled: true } }));\n```\n\n**@clerk/hono**\n```ts\napp.use('*', clerkMiddleware({ frontendApiProxy: { enabled: true } }));\n```\n\n**@clerk/fastify**\n```ts\nfastify.register(clerkPlugin, { frontendApiProxy: { enabled: true } });\n```\n\n**@clerk/backend**\n```ts\nimport { clerkFrontendApiProxy } from '@clerk/backend/proxy';\n```\n\nA quick way to check across your entire project:\n\n```sh\ngrep -r \"frontendApiProxy\\|clerkFrontendApiProxy\" .\n```\n\nIf there are no matches, you are not using this feature.\n\n\n## Recommended actions\n\nClerk'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.\n\n1. **Upgrade** to the patched version of `@clerk/backend` (and `@clerk/express`, `@clerk/hono`, etc.)\n2. **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](https://dashboard.clerk.com) under **API Keys**.  You should deploy your application with the updated key before revoking the existing key.\n3. **Audit access logs** for requests to your proxy endpoint (`/__clerk/` by default) containing double slashes in the path.\n\n\n\n## Credit\n\nDiscovered during an internal code audit.","published":"2026-04-01T16:59:21.828Z","modified":"2026-08-12T03:51:24.263149601Z","cvss":{"score":7.4,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"@clerk/backend","fixedVersion":"3.2.3"},{"ecosystem":"npm","name":"@clerk/express","fixedVersion":"2.0.7"},{"ecosystem":"npm","name":"@clerk/hono","fixedVersion":"0.1.5"},{"ecosystem":"npm","name":"@clerk/fastify","fixedVersion":"3.1.5"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34076.json"},{"type":"ADVISORY","url":"https://github.com/clerk/javascript/security/advisories/GHSA-gjxx-92w9-8v8f"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34076"},{"type":"PACKAGE","url":"https://github.com/clerk/javascript"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:24.263149601Z"}}