Individual skill
exploiting-subdomain-takeover-vulnerabilities
Identifying and exploiting dangling DNS records pointing to unclaimed cloud services, enabling subdomain takeover for phishing, cookie stealing, and authentication bypass during authorized penetration tests.
internal/tools/skills/data/web-application-security/exploiting-subdomain-takeover-vulnerabilities/SKILL.md
Source commit d42f381ad34843e71a42658e5c57290c713e85af
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- Observed behavior
- Network or broad shell
- Last checked
- Nov 9, 2026
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Repository context
- Repository stars (not skill ratings)
- 1,323
- Repository last updated
- Nov 9, 2026
- License
- Apache-2.0
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- cybersecurity Repository topic
- security Repository topic
- bug-bounty Repository topic
- automation Repository topic
- autonomous-pentesting Repository topic
- ai-agent Repository topic
- ai-security Repository topic
- ethical-hacking Repository topic
- golang Repository topic
- penetration-testing Repository topic
- penetration-testing Declared skill tag
- subdomain-takeover Declared skill tag
- dns Declared skill tag
- cloud-security Declared skill tag
- web-security Declared skill tag
- bug-bounty Declared skill tag
- security Derived category
- testing Derived category
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# Exploiting Subdomain Takeover Vulnerabilities
## When to Use
- During authorized penetration tests when subdomain enumeration reveals CNAME or A records pointing to external services
- When cloud service endpoints return "not found" or "no such bucket" error pages
- For assessing organizations with large subdomain footprints (100+ subdomains)
- When evaluating DNS hygiene and decommissioned service cleanup
- During bug bounty programs where subdomain takeover is in scope
### How to CONFIRM a Hit (avoid false negatives)
- **Positive signal**: the dangling CNAME/resource is **actually claimable** AND you serve your own content on it — confirm by claiming the resource with a **benign canary** and fetching the subdomain to see your marker, or by the third-party returning its specific **unclaimed fingerprint**.
- A `404` or generic error is NOT proof. Many services return 404 while still being owned/unclaimable; match the **exact service fingerprint** from `can-i-take-over-xyz`.