Detect Langflow IDOR: Unauthorized Access to Another User's Flow via /api/v1/responses in Elastic Security
CVE-2026-55255 is a critical IDOR (Insecure Direct Object Reference) vulnerability in Langflow versions prior to 1.9.1. An authenticated attacker can enumerate and access another user's flow data by manipulating object identifiers in requests to the /api/v1/responses endpoint. With a CVSS score of 9.9, this vulnerability allows horizontal privilege escalation between users, potentially exposing sensitive AI flow configurations, credentials embedded in flows, and proprietary automation logic.
MITRE ATT&CK
- Tactic
- Credential Access Collection
Elastic Detection Query
sequence by source.ip with maxspan=10m
[any where event.dataset == "http" and
url.path like "/api/v1/responses/*" and
http.response.status_code == 200] with runs=5Elastic EQL sequence detection identifying a single source IP making five or more successful requests to distinct /api/v1/responses paths within 10 minutes, indicating IDOR enumeration.
Data Sources
Required Tables
False Positives & Tuning
- High-throughput Langflow users legitimately accessing multiple flow results
- API clients performing batch result retrieval across user-owned flows
- Monitoring agents checking flow completion status at high frequency
- Load balancer health probes hitting the responses endpoint
Other platforms for CVE-2026-55255
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Unauthenticated Flow ID Discovery via /api/v1/responses
Expected signal: 20 GET requests to /api/v1/responses/* within seconds, all from the same source IP and Authorization header, appearing in web/application access logs
- Test 2Targeted Cross-User Flow Access Using Known Flow ID
Expected signal: Single authenticated GET request to /api/v1/responses/<victim_flow_id> returning HTTP 200 with flow response data belonging to a different user
- Test 3Scripted Flow Enumeration with Response Exfiltration
Expected signal: 50 GET requests to /api/v1/responses/* within approximately 30 seconds, with a subset returning HTTP 200 and response bodies containing flow data; all from single source IP
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