Rebinding Preview
A01 · ≈ 60 min · 0 solves
Explore the application as a real target: map the exposed functionality, inspect requests and responses, build a working exploit, and recover the rotating flag. If you get stuck, the verified official solution is available below as an optional spoiler.
Rules of engagement
Stay inside the generated lab URL. Use only the synthetic accounts and data in this instance. The main SecOne4all site and external systems are out of scope.
Challenge brief
What counts as a valid solve
Exploit a simulated DNS rebinding window between URL validation and connection.
GET /api/rebinding-preview?host={value}.
prove that the protected synthetic resource or action can be reached outside the intended account boundary; the successful workflow returns the current rotating flag.
Work only inside your generated lab URL and submit the flag within 60 minutes.
Official solution
Contains the complete exploitation path. Open it only when you want the spoiler.
Reveal official solutionStep-by-step · verified against the live lab
Official solution · A01 · Rebinding Preview
Objective
Exploit a simulated DNS rebinding window between URL validation and connection.
Steps
- Start the isolated lab and open its root page to confirm the scenario.
- Review the advertised starting endpoint and compare the trusted identity or object with the target described in the challenge.
- Send: GET /api/rebinding-preview?host=rebind.training.test
- Confirm the JSON response contains the rotating
flagfield. - Submit that exact flag on the SecOne4all challenge page before stopping or expiring the instance.
Expected proof
A successful response for ssrf-dns-rebinding returns the instance-specific rotating flag. The flag is valid only for the current player and running instance.
Safety boundary
Use only the generated lab URL. No request to the main site, another user, or an external service is part of this solution.