alert smtp any any -> [$HOME_NET,$HTTP_SERVERS,$SMTP_SERVERS] any (
msg:"ET EXPLOIT Exim New-Line Injection into Spool Header File Inbound - Information Disclosure Attempt (CVE-2020-28021)";
flow:established,to_server;
content:"MAIL|20|FROM";
content:"AUTH="; distance:0;
pcre:"/^.{0,100}\+0A.{0,100}\x40/R";
content:"+0A"; fast_pattern;
content:"|40|";
reference:url,www.qualys.com/2021/05/04/21nails/21nails.txt;
reference:cve,2020-28021;
classtype:attempted-admin;
sid:2032902; rev:1;
metadata:attack_target SMTP_Server, created_at 2021_05_04, cve CVE_2020_28021, deployment Perimeter, deployment Internal, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_05_04, mitre_tactic_id TA0007, mitre_tactic_name Discovery, mitre_technique_id T1082, mitre_technique_name System_Information_Discovery;
)