Detect Langflow IDOR: Unauthorized Access to Another User's Flow via /api/v1/responses in Sumo Logic CSE
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
Sumo Detection Query
_sourceCategory=web/access OR _sourceCategory=proxy/logs
| parse regex field=url "/api/v1/responses/(?<flow_id>[^/?\"]+)"
| where !isNull(flow_id)
| where status_code == "200" OR status == "200"
| timeslice 10m
| stats
count as request_count,
dcount(flow_id) as distinct_flow_ids,
makelist(flow_id) as flow_id_list
by src_ip, _timeslice, user_agent
| where distinct_flow_ids >= 5
| if(distinct_flow_ids >= 20, "critical", if(distinct_flow_ids >= 10, "high", "medium")) as severity
| sort by distinct_flow_ids descSumo Logic detection for CVE-2026-55255 IDOR pattern — parses Langflow /api/v1/responses requests, extracts flow IDs, and alerts when a single source enumerates five or more distinct IDs in a 10-minute window.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate bulk access by authenticated admin accounts reviewing platform-wide flows
- Automated CI/CD pipelines that trigger and poll multiple Langflow flow results
- Third-party integrations subscribed to multiple flow outputs via the API
- Langflow's own UI performing paginated result loading across many flows
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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