alert http any any -> [$HOME_NET,$HTTP_SERVERS] any (msg:"ET WEB_SPECIFIC_APPS Atlassian Unauthenticated Arbitrary File Read (CVE-2026-21589)"; flow:established,to_server; http.uri; content:"/download/resources/"; pcre:"/^.*?(?:(?:\x2e|%(?:25)*2[Ee]){1,2}(?:\x2f|\x5c|\x3a{2}|%(?:25)*5[Cc]|%(?:25)*2[Ff]|%(?:25)*3[aA]){1,}){2,}/R"; reference:url,labs.watchtowr.com/you-wont-hear-about-these-even-in-myths-atlassian-jira-confluence-and-more-pre-auth-arbitrary-file-read-cve-2026-21589/; reference:cve,2026-21589; classtype:attempted-user; sid:2072392; rev:1; metadata:affected_product Atlassian, attack_target Server, tls_state TLSDecrypt, created_at 2026_10_08, cve CVE_2026_21589, deployment Perimeter, deployment Internal, confidence High, signature_severity Major, tag Exploit, updated_at 2026_10_08, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application; target:dest_ip;)