alert http any any -> [$HOME_NET,$HTTP_SERVERS] any (msg:"ET EXPLOIT Nagios XI OS Command Injection (CVE-2021-25296)"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"nagiosxi/config/monitoringwizard.php?"; fast_pattern; content:"plugin_output_len="; pcre:"/^[0-9]{1,10}\x3b/R"; reference:cve,2021-25296; classtype:attempted-admin; sid:2034992; rev:1; metadata:attack_target Server, created_at 2022_01_27, cve CVE_2021_25296, deployment Perimeter, deployment Internal, confidence Medium, signature_severity Major, tag Exploit, tag CISA_KEV, updated_at 2022_01_27, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application;)