alert http any any -> [$HOME_NET,$HTTP_SERVERS] any (msg:"ET WEB_SPECIFIC_APPS Microsoft SharePoint JWT Token Authentication Bypass (CVE-2026-55040) M2"; flow:established,to_server; http.uri; content:"/_api/contextinfo"; fast_pattern; http.header; content:"Authorization|3a 20|Bearer|20|"; base64_decode:relative; base64_data; content:"|22|alg|22|"; pcre:"/^\s*\x3a\s*\x22none\x22/R"; reference:url,www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/; reference:cve,2026-55040; classtype:web-application-attack; sid:2071486; rev:1; metadata:affected_product Microsoft_Sharepoint, attack_target Server, tls_state TLSDecrypt, created_at 2026_08_12, cve CVE_2026_55040, deployment Perimeter, deployment Internal, confidence High, signature_severity Major, tag Exploit, updated_at 2026_08_12, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application; target:dest_ip;)