Inngest TypeScript SDK exposes environment variables via serve() handler on unhandled HTTP methods

Summary

A vulnerability in the Inngest TypeScript SDK versions 3.22.0 through 3.53.1 allows unauthenticated remote attackers to exfiltrate environment variables from the host process via the serve() HTTP handler.

The serve() handler implements GET, POST, and PUT methods. Requests using PATCH, OPTIONS, or DELETE fall through to a generic handler that returns diagnostic information. A change introduced in v3.22.0 caused this diagnostic response to include the contents of process.env, exposing any secrets, API keys, or credentials present in the environment.

Who is affected

An application is vulnerable if all of the following are true:

• It uses inngest SDK version >= 3.22.0, <= 3.53.1 (inclusive)
• Its serve() endpoint is reachable via PATCH, OPTIONS, or DELETE requests.

Please check your framework's implementation for the serve handler (documentation) to asses whether it handles these HTTP methods. Common vulnerable configurations include:

• Next.js Pages Router, which forwards all HTTP methods to the handler.
• Express via app.use('/api/inngest', serve(...)), which routes PATCH and OPTIONS to the handler by default.

The following are not affected:

• Next.js App Router handlers that explicitly export only GET, POST, and PUT.
• Applications using the connect worker method.
• SDK versions < 3.22.0 and >= 3.54.0, including all 4.x releases.

The vulnerability was responsibly disclosed by an Inngest user. At this time, there are no known reports of exploitation.

Remediation

1. Upgrade to inngest@3.54.0 or later. The fix is backwards compatible with the 3.x release line. The 4.x line is also unaffected.
2. Rotate any secrets that were presence in environment variables (process.env) within affected environments including Inngest signing keys and event keys
3. Search logs for any requests to your serve endpoints using the PATCH, OPTIONS, DELETE http methods to assess if any environment variables may have been exposed.

Additional recommendations

Users on platforms with long-lived deployments (e.g. Vercel, Cloudflare Workers) should be aware that prior deployments remain reachable at their immutable URLs and may continue to expose the vulnerability even after a new deployment is promoted. For example, Vercel offers security features such as "Deployment Protection" and the ability to delete older deployments which can help immediately mitigate impact.

For additional security, users can also adjust firewall or proxy rules to only allow requests to their serve endpoint from Inngest IP addresses available here: http://inngest.com/ips-v4, http://inngest.com/ips-v6

Workarounds

If upgrading is not immediately possible, restrict the serve() endpoint at the framework or reverse-proxy layer to accept only GET, POST, and PUT. The Inngest serve() endpoint does not require any other HTTP methods.

Resources

• Rotating Inngest keys: https://www.inngest.com/docs/platform/manage/rotating-keys
• Inngest signing keys: https://www.inngest.com/docs/platform/signing-keys
• Inngest event keys: https://www.inngest.com/docs/events/creating-an-event-key
• Inngest security best practices: https://www.inngest.com/docs/learn/security

Credits

• Ben Hylak - an independent security researcher, discovered and responsibly disclosed the vulnerability.