ET WEB_SPECIFIC_APPS Advantech R-SeeNet ping.php Command Injection (CVE-2021-21805)

alert http any any -> $HOME_NET any (
    msg:"ET WEB_SPECIFIC_APPS Advantech R-SeeNet ping.php Command Injection (CVE-2021-21805)";
    flow:established,to_server;
    http.uri;
    content:"/php/ping.php|3f|"; fast_pattern;
    content:"hostname|3d|";
    pcre:"/^[^&$]*?(?:[\x3b\x24\x60\x7c]|\x25(?:3[bB]|24|60|7[cC]))/R";
    http.method;
    content:"GET";
    reference:url,www.talosintelligence.com/vulnerability_reports/TALOS-2021-1274;
    reference:cve,2021-21805;
    classtype:web-application-attack;
    sid:2065739; rev:1;
    metadata:attack_target Server, tls_state TLSDecrypt, created_at 2025_11_12, cve CVE_2021_21805, deployment Perimeter, deployment Internal, deployment SSLDecrypt, confidence High, signature_severity Major, tag Exploit, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2025_11_12, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application;
    target:dest_ip;
)