ET WEB_SPECIFIC_APPS n8n Ni8mare Content-Type Confusion Multipart Form Bypass (CVE-2026-21877) M1

Query · suricata

flow:established,to_server;
http.request_body;
content:"|22|executionId|22 3a|"; fast_pattern;
content:"|22|files|22 3a|";
content:"|22|filepath|22 3a|";
pcre:"/^\s*\x22[^\x22]*?\x2f/R";
http.uri;
content:"/form/"; startswith;
http.content_type;
content:"application/json";
http.method;
content:"POST";
target:dest_ip;
Raw source ET WEB_SPECIFIC_APPS n8n Ni8mare Content-Type Confusion Multipart Form Bypass (CVE-2026-21877) M1 · Suricata
Esc
Published by Emerging Threats Open ↗, licensed under BSD 3-Clause ↗. Line breaks added for readability; the rule is otherwise unchanged. 
alert http any any -> $HOME_NET any (
    msg:"ET WEB_SPECIFIC_APPS n8n Ni8mare Content-Type Confusion Multipart Form Bypass (CVE-2026-21877) M1";
    flow:established,to_server;
    http.request_body;
    content:"|22|executionId|22 3a|"; fast_pattern;
    content:"|22|files|22 3a|";
    content:"|22|filepath|22 3a|";
    pcre:"/^\s*\x22[^\x22]*?\x2f/R";
    http.uri;
    content:"/form/"; startswith;
    http.content_type;
    content:"application/json";
    http.method;
    content:"POST";
    reference:url,www.cyera.com/research-labs/ni8mare-unauthenticated-remote-code-execution-in-n8n-cve-2026-21858;
    reference:cve,2026-21877;
    classtype:web-application-attack;
    sid:2066610; rev:1;
    metadata:attack_target Server, tls_state TLSDecrypt, created_at 2026_01_07, cve CVE_2026_21877, deployment Perimeter, deployment Internal, deployment SSLDecrypt, confidence High, signature_severity Major, tag Exploit, updated_at 2026_01_07, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application;
    target:dest_ip;
)

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