Dangling cname that missed by a lot of Hackers

I'm gone share with you one of my findings Today that missed by a lot of hackers, by using some RECON and tools i find juice bug in (soundcloud,Netflix,Dropbox,hubspot,linktree,Riot,etc…..)

Summary:

During my reconnaissance on the target domain, I discovered a dangling CNAME record that allowed me to perform a subdomain takeover on `inbox.example.com.` This misconfiguration could let an attacker impersonate the organization's email infrastructure and send phishing or malicious emails from a legitimate-looking domain

While performing subdomain enumeration on the main domain (example.com), I found several subdomains and checked their DNS configurations. One of them, inbox.example.com, was pointing to a third-party service that was not claimed by the organization.

When I attempted to claim this subdomain through the hosting provider, BOOMM I was able to successfully take ownership of the resource and able to send or receive emails

After claiming it, I could configure it to send and receive emails from the address:

`anything@inbox.example.com`

This allowed me to send legitimate-looking emails on behalf of the organization's domain, posing a significant phishing and spoofing risk.

Steps to Reproduce

1. Enumerate subdomains for example.com using tools such as subfinder, amass, or assetfinder.

2. Identify the DNS record for inbox.example.com.

inbox.example.com CNAME some-service.hostingprovider.com

3. Verify that the CNAME target (some-service.hostingprovider.com) is unclaimed or inactive.

4. Create an account on the corresponding hosting provider and claim the subdomain.

5. Confirm control by hosting a custom page or sending an email using anything@inbox.example.com.

Recommendation

Regularly audit DNS records to identify and remove unused or orphaned CNAME entries.

Use automation tools to detect dangling records.

Implement domain verification and ownership monitoring for all third-party integrations.

wait for another writeups,

Ahmed