CISA has added a critical IDOR vulnerability in Langflow (CVE-2026-55255) to its KEV catalog, requiring immediate patching for all deployments prior to version 1.9.2.
CVE-2026-55255 represents a critical security failure in Langflow, an AI-agent deployment and orchestration framework. Classified as an Insecure Direct Object Reference (IDOR) under CWE-639, the vulnerability allows authenticated users to bypass authorization controls and interact with workflows owned by other users. Given its active exploitation in the wild, CISA has officially added this flaw to its Known Exploited Vulnerabilities (KEV) Catalog. The criticality is underscored by a CVSS 3.1 base score of 8.4, necessitating immediate remediation to maintain compliance with BOD 22-01 and BOD 26-04.
The vulnerability exists within the application's API architecture, specifically at the /api/v1/responses endpoint. Langflow, which functions as a low-code UI for managing complex AI-powered agent workflows, relies on internal identifiers to map execution requests to specific user-owned flow objects.
In affected versions (prior to 1.9.2), the application fails to perform adequate server-side validation of ownership when a user submits a flow execution request. The vulnerability follows the classic IDOR pattern: an authenticated attacker can identify a victim’s flow_id and inject it into a request directed at the /api/v1/responses endpoint. Because the application logic trusts the user-supplied identifier without verifying that the requesting user maintains authorized access to that specific object, it proceeds to execute the workflow on behalf of the attacker.
The CVSS vector CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L illustrates a high-impact scenario. The 'Scope: Changed' (S:C) attribute indicates that the vulnerability allows an attacker to impact resources beyond the intended sandbox, leading to a significant loss of Confidentiality (C:H) and Integrity (I:H).
The exploitation mechanism involves manipulating standard API requests intended for legitimate workflow execution. Practitioners should inspect ingress logs for anomalous traffic directed at /api/v1/responses where the flow_id parameter does not align with expected user session telemetry.
Defensive posturing requires strict API access control lists (ACLs). Ensure that every request to the backend validation layer checks the association between the authenticated session token (or User ID) and the requested flow_id resource in the database schema. Any mismatch must trigger an immediate 403 Forbidden response. Furthermore, utilize rate limiting and audit logging on this endpoint to detect enumeration attempts, as attackers often iterate through sequential ID numbers to identify valid targets.
The maintainers have addressed this flaw in version 1.9.2. All organizations currently deploying Langflow in production must prioritize the following steps:
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