ET EXPLOIT free5GC UDR Fail-Open Abuse - Truncated JSON (CVE-2026-40343)

alert http any any -> $HOME_NET any (
    msg:"ET EXPLOIT free5GC UDR Fail-Open Abuse - Truncated JSON (CVE-2026-40343)";
    flow:established,to_server;
    http.uri;
    content:"/nudr-dr/v2/policy-data/subs-to-notify"; fast_pattern;
    http.content_type;
    content:"application/json";
    http.request_body;
    pcre:"/^\x7b(?:(?!\x7d$).)+$/";
    reference:url,dev.to/cverports/cve-2026-40343-cve-2026-40343-fail-open-request-handling-in-free5gc-udr-policy-data-subscription-5hb4;
    reference:cve,2026-40343;
    classtype:web-application-attack;
    sid:2068970; rev:1;
    metadata:attack_target Server, tls_state TLSDecrypt, created_at 2026_04_24, cve CVE_2026_40343, deployment Perimeter, deployment Internal, deployment SSLDecrypt, confidence High, signature_severity Major, tag Exploit, updated_at 2026_04_24, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application;
    target:dest_ip;
)