ET HUNTING SonicWall Email Security Unauthenticated Arbitrary User Creation (CVE-2021-20021) M2

alert http any any -> $HOME_NET any (
    msg:"ET HUNTING SonicWall Email Security Unauthenticated Arbitrary User Creation (CVE-2021-20021) M2";
    flow:established,to_server;
    http.uri; bsize:9;
    content:"/createou"; fast_pattern; startswith;
    http.request_body;
    content:"data|3d|";
    http.method;
    content:"POST";
    reference:url,cloud.google.com/blog/topics/threat-intelligence/zero-day-exploits-in-sonicwall-email-security-lead-to-compromise;
    reference:cve,2021-20021;
    classtype:web-application-attack;
    sid:2064935; rev:1;
    metadata:affected_product SonicWall, attack_target Server, tls_state TLSDecrypt, created_at 2025_09_26, cve CVE_2021_20021, deployment Perimeter, deployment Internal, deployment SSLDecrypt, confidence High, signature_severity Major, tag Exploit, updated_at 2025_09_26, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application;
    target:dest_ip;
)