Clerk patches SSRF that leaks Clerk-Secret-Key
TL;DR — A High-severity SSRF in Clerk’s clerkFrontendApiProxy can leak an application’s Clerk-Secret-Key to an attacker-controlled host via a crafted request path.
What happened
Clerk is an authentication/identity platform; the @clerk/* server SDKs are used in backend services to integrate Clerk auth and related API calls.
CVE-2026-34076 (GitHub CNA publication) reports that the clerkFrontendApiProxy function in @clerk/backend is vulnerable to Server-Side Request Forgery (SSRF). Per the CVE record, 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.
Severity is CVSS v3.1 7.4 (High). SSRF in proxy/helper code is a high-signal class because it often turns “just routing” logic into a secret-exfiltration primitive when backend credentials are attached to outbound requests.
Who is impacted
- Deployments using affected versions of Clerk’s JavaScript server SDKs where the opt-in
clerkFrontendApiProxybehavior is reachable.
| Component | Affected versions (per CVE record) | Patched versions (per CVE record) |
|---|---|---|
@clerk/hono | >= 0.1.0, < 0.1.5 | 0.1.5 |
@clerk/express | >= 2.0.0, < 2.0.7 | 2.0.7 |
@clerk/backend | >= 3.0.0, < 3.2.3 | 3.2.3 |
@clerk/fastify | >= 3.1.0, < 3.1.5 | 3.1.5 |
What to do now
- Follow vendor remediation guidance and apply the patched releases described in the CVE record.
-
"This issue has been patched in @clerk/hono version 0.1.5, @clerk/express version 2.0.7, @clerk/backend version 3.2.3, and @clerk/fastify version 3.1.5."
-
- Inventory services that depend on
@clerk/backend,@clerk/express,@clerk/fastify, or@clerk/hono, and confirm whetherclerkFrontendApiProxyis enabled/reachable in production request paths. - Treat potential
Clerk-Secret-Keyexposure as a credential incident: if you suspect abuse (unexpected outbound requests, suspicious proxy paths, or unknown hosts receiving traffic), rotate the affected application secret and review egress logs around the proxy feature.
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