CVE-2026-33484: Langflow Auth Bypass Vulnerability

CVE-2026-33484 Overview

CVE-2026-33484 is a Broken Access Control vulnerability affecting Langflow, a tool for building and deploying AI-powered agents and workflows. The vulnerability exists in the /api/v1/files/images/{flow_id}/{file_name} endpoint, which serves image files without any authentication or ownership verification. This allows any unauthenticated attacker to access sensitive user-uploaded images by simply knowing or guessing the flow_id and file_name parameters.

Critical Impact

In multi-tenant deployments, attackers who can discover or guess a flow_id (UUIDs can be leaked through other API responses) can download any user's uploaded images without credentials, potentially exposing sensitive AI workflow data, proprietary images, and confidential information.

Affected Products

• Langflow versions 1.0.0 through 1.8.1
• Langflow multi-tenant deployments
• Any Langflow instance exposing the /api/v1/files/images/ endpoint

Discovery Timeline

• 2026-03-24 - CVE-2026-33484 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-33484

Vulnerability Analysis

This vulnerability is classified under CWE-284 (Improper Access Control), which occurs when an application fails to properly restrict access to a resource from an unauthorized actor. In this case, the Langflow image serving endpoint completely bypasses authentication and authorization checks, creating a direct path for unauthorized data access.

The vulnerability is particularly concerning in multi-tenant environments where multiple users or organizations share the same Langflow instance. The attack can be conducted remotely over the network without any user interaction or privileges required. The primary impact is confidentiality compromise, as attackers can exfiltrate user-uploaded images containing potentially sensitive data related to AI workflows and business processes.

Root Cause

The root cause of CVE-2026-33484 lies in the missing authentication and authorization middleware on the /api/v1/files/images/{flow_id}/{file_name} endpoint. The endpoint was implemented to serve static image files but failed to:

1. Verify that the requesting user is authenticated
2. Validate that the authenticated user owns the specified flow_id
3. Implement any access control checks before returning the file content

This design flaw allows direct object reference without ownership verification, enabling horizontal privilege escalation across user boundaries.

Attack Vector

The attack vector is network-based and requires no authentication. An attacker can exploit this vulnerability by:

1. UUID Discovery: Obtaining valid flow_id values through API response enumeration, error message disclosure, or brute-forcing UUID patterns
2. File Enumeration: Once a valid flow_id is obtained, common filename patterns can be tested against the endpoint
3. Data Exfiltration: Successful requests return HTTP 200 with the image content, allowing bulk download of user files

The vulnerability requires only network access to the Langflow instance. In scenarios where flow_id UUIDs are leaked through other API responses or can be predicted, exploitation becomes trivial. See the GitHub Security Advisory for additional technical details.

Detection Methods for CVE-2026-33484

Indicators of Compromise

• Unusual volume of requests to /api/v1/files/images/ endpoints from unauthenticated sources
• Sequential or pattern-based requests attempting to enumerate flow_id UUIDs
• HTTP 200 responses to the images endpoint from IP addresses not associated with legitimate users
• Access logs showing image downloads without corresponding authentication tokens

Detection Strategies

• Monitor web server access logs for requests to /api/v1/files/images/ without valid session cookies or authentication headers
• Implement rate limiting detection on the images endpoint to identify enumeration attempts
• Deploy Web Application Firewall (WAF) rules to flag suspicious UUID patterns in request paths
• Create alerts for successful image access from new or untrusted IP addresses

Monitoring Recommendations

• Enable detailed access logging for all Langflow API endpoints with IP address and user-agent tracking
• Implement anomaly detection for unusual patterns of image endpoint access
• Set up real-time alerting for high-volume requests to file serving endpoints
• Review authentication logs for correlation between image access and valid user sessions

How to Mitigate CVE-2026-33484

Immediate Actions Required

• Upgrade Langflow to version 1.9.0 or later immediately
• Audit access logs to identify any potential exploitation prior to patching
• Review any sensitive images that may have been exposed in multi-tenant deployments
• Consider rotating or replacing any confidential data contained in previously uploaded images

Patch Information

Langflow version 1.9.0 contains the security patch that addresses this vulnerability. The fix implements proper authentication and ownership verification on the /api/v1/files/images/{flow_id}/{file_name} endpoint. Organizations should upgrade from any version in the affected range (1.0.0 through 1.8.1) to version 1.9.0 or later.

For detailed patch information, refer to the Langflow Security Advisory on GitHub.

Workarounds

• Place Langflow behind a reverse proxy with authentication requirements for all /api/v1/files/ paths
• Restrict network access to Langflow instances using firewall rules to limit exposure to trusted networks only
• Implement IP allowlisting for API access if upgrading immediately is not possible
• Consider taking multi-tenant deployments offline until the patch can be applied if sensitive data is at risk

# Example nginx configuration to require authentication for image endpoints
# Add to your nginx server block as a temporary workaround
location /api/v1/files/images/ {
    auth_basic "Restricted Access";
    auth_basic_user_file /etc/nginx/.htpasswd;
    proxy_pass http://langflow_backend;
}