AI BriefingCloudflare Launches PHP Capture the Flag Challenge to Test WAF Defenses Against php2shell Vulnerabilities
·2026.10.27 22:00
Key point
The challenge targets a stock PHP 8.5.11 environment protected by Cloudflare WAF rules, requiring researchers to achieve remote code execution and recover a flag via HackerOne.
Details
- Cloudflare launched a limited-time Capture the Flag (CTF) challenge via its Bug Bounty program on HackerOne to test WAF protections against the php2shell vulnerabilities (CVE-2026-109618 and CVE-2026-109619).
- The target is a deliberately vulnerable PHP 8.5.11 installation running Apache 2 (mod_php) inside a Cloudflare Container, with default WAF rules enabled; the sandbox resets every few minutes.
- Participants must demonstrate attacker-controlled PHP code execution via an authorized POST request, recover the contents of /flag, and verify it through the CTF UI before submitting a private report to Cloudflare.
- Eligible submissions require a materially distinct bypass method or exploit payload; rediscovery of known vulnerabilities, local-only exploits, or RCE without successful flag recovery are not eligible for bounties.
- The challenge is authorized only for the /php/* endpoints on the challenge hostname; testing other Cloudflare services, direct infrastructure access, or denial-of-service attacks is out of scope.
- Cloudflare emphasizes that WAF protection is not a substitute for patching and advises PHP users to apply the latest security updates.
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