CVE-2025-26319: Flowiseai Flowise Path Traversal Flaw

CVE-2025-26319 Overview

CVE-2025-26319 is an arbitrary file upload vulnerability discovered in FlowiseAI Flowise version 2.2.6. The vulnerability exists in the /api/v1/attachments endpoint, which fails to properly validate uploaded files. This weakness allows unauthenticated attackers to upload malicious files to the server, potentially leading to remote code execution and complete system compromise.

FlowiseAI Flowise is an open-source low-code tool for developers to build customized LLM orchestration flows and AI agents. The platform's popularity in AI/ML development environments makes this vulnerability particularly concerning, as compromised instances could provide attackers access to sensitive AI models, training data, and associated infrastructure.

Critical Impact

This arbitrary file upload vulnerability allows unauthenticated remote attackers to upload malicious files via the /api/v1/attachments endpoint, potentially enabling remote code execution with no user interaction required.

Affected Products

• FlowiseAI Flowise version 2.2.6
• Potentially earlier versions of FlowiseAI Flowise (unconfirmed)

Discovery Timeline

• March 4, 2025 - CVE-2025-26319 published to NVD
• June 24, 2025 - Last updated in NVD database

Technical Details for CVE-2025-26319

Vulnerability Analysis

This vulnerability is classified as CWE-434 (Unrestricted Upload of File with Dangerous Type). The /api/v1/attachments endpoint in FlowiseAI Flowise 2.2.6 does not implement adequate file type validation or sanitization mechanisms. When users or automated processes upload files through this API endpoint, the application fails to verify the file's content, extension, or MIME type against an allowlist of safe file types.

The network-based attack vector requires no authentication or user interaction, making exploitation straightforward for remote attackers. An attacker can craft a malicious payload disguised as a legitimate attachment and upload it directly to the vulnerable endpoint. Depending on the server configuration and how uploaded files are processed or stored, this could result in:

• Remote code execution if uploaded scripts are executed by the server
• Web shell deployment for persistent backdoor access
• Overwriting critical system files if path traversal is also possible
• Serving malicious content to other users of the platform

Root Cause

The root cause of CVE-2025-26319 lies in insufficient input validation within the file upload handling logic of the /api/v1/attachments endpoint. The application does not enforce proper restrictions on:

1. File type verification based on content analysis (magic bytes)
2. File extension validation against a secure allowlist
3. MIME type validation
4. File size limits that could prevent denial of service attacks

This lack of defense-in-depth allows attackers to bypass any superficial client-side checks and upload arbitrary file types directly to the server.

Attack Vector

The attack is network-based and requires no authentication or privileges. An attacker can exploit this vulnerability by sending a crafted HTTP POST request to the /api/v1/attachments endpoint containing a malicious file payload. The attack flow typically involves:

1. Identifying a vulnerable FlowiseAI Flowise instance exposed to the network
2. Crafting a malicious file (e.g., web shell, reverse shell script, or executable)
3. Sending a multipart form-data POST request to /api/v1/attachments with the malicious file
4. Accessing the uploaded file to trigger code execution or achieve other malicious objectives

For detailed technical information regarding exploitation, refer to the CVE-2025-26319 PoC Repository.

Detection Methods for CVE-2025-26319

Indicators of Compromise

• Unusual files with executable extensions (.php, .jsp, .py, .sh, .exe) appearing in attachment storage directories
• Unexpected HTTP POST requests to /api/v1/attachments from external or untrusted IP addresses
• Web shell signatures or known malicious file hashes in uploaded content
• Anomalous process execution originating from the Flowise application directory

Detection Strategies

• Implement Web Application Firewall (WAF) rules to inspect file upload requests for malicious content and dangerous file types
• Deploy file integrity monitoring on directories where uploaded attachments are stored
• Configure application-layer logging to capture all requests to /api/v1/attachments including source IPs, file names, and sizes
• Use YARA rules or antivirus scanning on uploaded files to detect known malicious payloads

Monitoring Recommendations

• Enable detailed access logging for all API endpoints, particularly /api/v1/attachments
• Set up alerts for file uploads with suspicious extensions or unusually large sizes
• Monitor server processes for unexpected child processes spawned by the Flowise application
• Track outbound network connections from the Flowise server that could indicate reverse shell activity

How to Mitigate CVE-2025-26319

Immediate Actions Required

• Restrict network access to FlowiseAI Flowise instances using firewall rules or VPN requirements
• Implement authentication requirements for the /api/v1/attachments endpoint if not already enforced
• Deploy a reverse proxy with file upload filtering capabilities in front of the Flowise application
• Audit existing uploaded files for any signs of compromise or malicious content

Patch Information

Organizations should monitor the official FlowiseAI Flowise repository for security patches addressing CVE-2025-26319. Check the CVE-2025-26319 PoC Repository for additional remediation guidance and to stay informed about patch availability. Upgrade to a patched version as soon as one becomes available from the vendor.

Workarounds

• Implement a strict allowlist of permitted file extensions at the web server or reverse proxy level
• Configure the web server to prevent execution of uploaded files by disabling script handlers in upload directories
• Add file content validation (magic byte checking) at the application layer or via middleware
• Consider temporarily disabling the attachment upload functionality if it is not critical to operations

# Example nginx configuration to restrict file types and prevent execution
location /api/v1/attachments {
    # Limit allowed file types via client_body_temp_path processing
    client_max_body_size 10M;
    
    # Disable script execution in upload directory
    location ~* ^/uploads/.*\.(php|jsp|py|sh|exe|bat|cmd)$ {
        deny all;
        return 403;
    }
}