ET WEB_SPECIFIC_APPS Ivanti EPM Cloud Services Appliance Backdoor Access Attempt (CVE-2021-44529)

alert http any any -> $HOME_NET any (
    msg:"ET WEB_SPECIFIC_APPS Ivanti EPM Cloud Services Appliance Backdoor Access Attempt (CVE-2021-44529)";
    flow:established,to_server;
    flowbits:set,ET.CVE-2021-44529.Request;
    http.method;
    content:"GET";
    http.uri;
    content:"/client/index.php";
    http.cookie;
    content:"|3d|ab|3b 20|"; fast_pattern;
    pcre:"/^.+(?:c3lzdGVt|N5c3Rlb|zeXN0ZW|PD9waH|w\x2fcGhw|8P3Boc|cGhwaW5mb|BocGluZm|waHBpbmZv)/R";
    reference:url,attackerkb.com/topics/XTKrwlZd7p/cve-2021-44529;
    reference:cve,2021-44529;
    classtype:attempted-admin;
    sid:2059891; rev:2;
    metadata:affected_product Ivanti, attack_target Networking_Equipment, tls_state TLSDecrypt, created_at 2025_02_05, cve CVE_2021_44529, deployment Perimeter, deployment Internal, deployment SSLDecrypt, performance_impact Low, confidence High, signature_severity Major, tag Exploit, tag CISA_KEV, updated_at 2025_07_10, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application;
    target:dest_ip;
)