alert http any any -> [$HOME_NET,$HTTP_SERVERS] any (msg:"ET EXPLOIT Apache HTTP Server SSRF (CVE-2021-40438)"; flow:established,to_server; urilen:>200; http.method; content:"GET"; http.uri; content:"/?unix|3a|"; nocase; fast_pattern; content:"|7c|http"; reference:cve,2021-40438; classtype:attempted-admin; sid:2034566; rev:2; metadata:attack_target Server, created_at 2021_11_30, cve CVE_2021_40438, deployment Perimeter, deployment Internal, confidence High, signature_severity Major, tag Exploit, tag CISA_KEV, updated_at 2021_11_30, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application;)