Cloudflare Patches WAF ACME Validation Bypass
Cloudflare patched a flaw in its web application firewall on October 27 that allowed attackers to bypass WAF rules and directly access origin servers. FearsOff researchers reported the ACME HTTP-01 validation logic bug in October; Cloudflare says customers need not take action after it corrected token-hostname verification. The issue could have enabled data theft or server takeover and raises concerns about automated, AI-driven exploitation.
Key Points
- 1Patched WAF bypass allowing attackers to reach origin servers via ACME HTTP-01 token path.
- 2Logic failed to verify hostname-token association, causing WAF features to be disabled for some requests.
- 3Review ACME endpoints and monitoring; attackers and AI tools could enumerate /.well-known/acme-challenge/ at scale.
Scoring Rationale
High operational impact across many customers due to an official Cloudflare patch, limited by being a single-vendor logic bug.
Sources
Public references used for this report.
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