CVE-2026-34076: Clerk SSRF Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gjxx-92w9-8v8f",
  "modified" : "2026-04-06T16:44:03Z",
  "published" : "2026-03-27T19:58:19Z",
  "aliases" : [ "CVE-2026-34076" ],
  "summary" : "Clerk: 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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@clerk/backend"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.0.0"
      }, {
        "fixed" : "3.2.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.2.2"
    }
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@clerk/express"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0"
      }, {
        "fixed" : "2.0.7"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.0.6"
    }
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@clerk/hono"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.1.0"
      }, {
        "fixed" : "0.1.5"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.1.4"
    }
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@clerk/fastify"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.1.0"
      }, {
        "fixed" : "3.1.5"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.1.4"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-918" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-27T19:58:19Z",
    "nvd_published_at" : "2026-04-01T18:16:29Z"
  }
}