HIGH SEVERITYCMSCVSS 8.6Immediate (<90s)ID: readme-io
Readme.io Dangling DNS & Takeover Fingerprint
Documentation CNAME points to an unclaimed or deleted Readme project. Anyone can register the matching project subdomain on Readme.io.
DNS CNAME Delegation Rules
*.readme.io
CNAME points to readme.io. Returns 'Project doesnt exist yet'.
404 Not Found
Authoritative Response Token
“Project doesnt exist yet”
curl -sI http://subdomain.example.com | grep 'Project doesnt exist yet'When SubdomainWatch scanner identifies this response on an unresolved CNAME target, an automated alert is triggered within 800ms.
Remediation Guide & Defensive Action Plan
Immediate Action Required: Delete the CNAME pointing to Readme.io or configure the project slug within your Readme.io dashboard.
Defensive Verification Checklist:
- Audit authoritative DNS zone records for any CNAME pointing to
*.readme.io. - Verify whether the target resource or bucket still exists under your organization's cloud tenant.
- If decommissioned, delete the DNS record immediately to close the public exposure window.
- Deploy a pre-merge IaC security gate (such as SubdomainWatch Takeover Guard) to intercept dangling records before pull requests merge.
Terraform Remediation Example
# Remove Readme.io CNAME
ATTACK SURFACE DETECTION COMPARISON
Why Static DNS Scanners Miss Readme.io Takeovers
Passive DNS repositories like SecurityTrails and heavy scanners like Detectify record domain records retrospectively or trigger alert fatigue. SubdomainWatch conducts active recursive CNAME testing with zero false positives.
Readme.io Takeover FAQs
Yes. Attackers can publish fraudulent API keys, endpoints, or documentation redirecting developer credentials.
FREE UNRESTRICTED SCANNER
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