Subdomain takeover of fr1.vpn.zomans.com

How it was found

Summary

fr1.vpn.zomans.com points to an AWS EC2 instance at 52.47.57.107 that no longer exists. I was able to take control of this IP address and run my own EC2 instance. I can now serve content on this domain, obtain a TLS certificate for this domain, etc.

If any customers or servers are pointing to anything within this domain, I could serve them arbitrary/malicious content. I could also use this in case your domain whitelists your own domain for OAuth, or if there are cookies scoped to the entire domain. Usually this can have a high impact.

Since the risk of employee phishing here is pretty high, along with the risk of existing clients connecting to this server, I think it qualifies as a High per your policy:

Subdomain Takeover - on a domain that sees heavy traffic or would be a convincing candidate for a phishing attack

PoC

% dig +short fr1.vpn.zomans.com
52.47.57.107

% curl fr1.vpn.zomans.com
<!-- hackerone.com/ian -->

Impact

Subdomain takeover