Langflow /api/v1/responses IDOR Vulnerability Leading to Unauthorized Flow Execution (CVE-2026-55255)

1. Apply Official Security Patch

The recommended remediation is to upgrade Langflow to version 1.9.1 or later.

# If using pip
pip install --upgrade langflow

# If using Docker, pull and redeploy the latest image
docker pull langflowai/langflow:latest

2. Temporary Mitigations

• Network Access Control: Restrict access to the Langflow dashboard and API endpoints using firewalls or VPNs, ensuring they are not exposed to the public internet.
• WAF Rules: Implement Web Application Firewall (WAF) rules to monitor and block anomalous or repetitive requests targeting the /api/v1/responses endpoint.

Langflow is an open-source tool designed for building and deploying AI-powered agents and workflows. This vulnerability (CVE-2026-55255) is an Insecure Direct Object Reference (IDOR, CWE-639) located in the /api/v1/responses endpoint.

Exploit Mechanics

The application fails to validate whether the authenticated user making the request has the authorization to access or execute the requested resource (Flow ID). An attacker with low-privileged access can manipulate the flow_id parameter in the API request to target a victim's flow, triggering unauthorized execution.

Impact & Severity

With a CVSS score of 8.4 (High) and its inclusion in the CISA Known Exploited Vulnerabilities (KEV) catalog, this vulnerability is actively being exploited in the wild. Successful exploitation can lead to the exposure of sensitive credentials, API keys, database connections, or proprietary LLM prompts integrated within the victim's workflow.