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Subdomain Takeover Scanner - DNS & CNAME Vulnerability Audit Tool
Detect dangling DNS records and vulnerable CNAME pointers across GitHub Pages, AWS S3, Azure, and Cloudflare to prevent domain hijacking.
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Continue to Free Tool / Download →Preventing Subdomain Takeover Vulnerabilities in DNS Records
A subdomain takeover occurs when a canonical name (CNAME) record points to an external cloud asset (such as an expired AWS S3 bucket, GitHub Pages repo, or Heroku slug) that has been deleted by the owner but remains claimable by an unauthorized third party.
Common Vulnerable Cloud Providers
| Cloud Service | DNS Pattern | Remediation Step |
|---|---|---|
| AWS S3 Bucket | [name].s3.amazonaws.com | Delete dangling CNAME or re-create bucket |
| GitHub Pages | [org].github.io | Bind custom domain in repository settings |
| Heroku App | [app].herokuapp.com | Remove DNS record if instance is decommissioned |
How to Audit Your DNS Records
dig CNAME sub.yourdomain.com +short
# Check HTTP status code and signature string
curl -Iv https://sub.yourdomain.comIf the response returns a 404 with service-specific claim prompts, the pointer must be immediately purged from your DNS zone editor.
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