CVE-2026-6596 Overview
A security flaw has been discovered in langflow-ai Langflow up to version 1.1.0. This issue affects the function create_upload_file of the file src/backend/base/Langflow/api/v1/endpoints.py of the component API Endpoint. The manipulation results in unrestricted upload. It is possible to launch the attack remotely. The exploit has been released to the public and may be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.
Critical Impact
Remote attackers can exploit the unrestricted file upload vulnerability to upload malicious files to the server, potentially leading to remote code execution, server compromise, or other malicious activities.
Affected Products
- langflow-ai Langflow versions up to 1.1.0
- Langflow API Endpoint component
- Systems running vulnerable create_upload_file function
Discovery Timeline
- 2026-04-20 - CVE CVE-2026-6596 published to NVD
- 2026-04-22 - Last updated in NVD database
Technical Details for CVE-2026-6596
Vulnerability Analysis
This vulnerability is classified under CWE-284 (Improper Access Control), specifically manifesting as an unrestricted file upload weakness in the Langflow API. The affected component is the create_upload_file function located within the API endpoint module at src/backend/base/Langflow/api/v1/endpoints.py.
The vulnerability allows remote attackers to upload arbitrary files to the server without proper validation or restrictions. This type of flaw is particularly dangerous in AI/ML workflow platforms like Langflow, as it can be leveraged to upload executable scripts, web shells, or other malicious payloads that could compromise the underlying server infrastructure.
The attack can be executed remotely over the network without requiring any prior authentication or user interaction, making it accessible to unauthenticated attackers. A proof-of-concept exploit has been publicly released, increasing the risk of active exploitation.
Root Cause
The root cause of this vulnerability lies in improper access control within the file upload handling mechanism. The create_upload_file function fails to implement adequate validation checks for uploaded files. This includes missing or insufficient verification of file types, file extensions, file content, and upload destination paths. The lack of proper sanitization allows attackers to bypass intended security restrictions and upload potentially dangerous files to the server.
Attack Vector
The attack vector is network-based, allowing remote exploitation. An attacker can craft malicious HTTP requests targeting the vulnerable API endpoint to upload arbitrary files. The attack flow typically involves:
- Identifying the vulnerable Langflow instance exposed to the network
- Crafting a file upload request to the /api/v1/ endpoint
- Uploading a malicious file (such as a web shell or script) without validation
- Potentially executing the uploaded payload to gain further access
Technical details and proof-of-concept code are available through the GitHub Gist PoC Example and additional vulnerability information can be found at VulDB #358231.
Detection Methods for CVE-2026-6596
Indicators of Compromise
- Unusual file upload activity to the Langflow API endpoints, particularly files with executable extensions (.py, .sh, .php, .jsp)
- New or unexpected files appearing in upload directories or web-accessible paths
- HTTP POST requests to /api/v1/ endpoints containing suspicious file content or unusual MIME types
- Web server logs showing repeated file upload attempts from unknown or suspicious IP addresses
Detection Strategies
- Implement file integrity monitoring (FIM) on directories where Langflow stores uploaded files to detect unauthorized additions
- Configure web application firewall (WAF) rules to inspect and block file upload requests containing executable file types or suspicious content
- Monitor API request logs for anomalous patterns such as high-volume upload requests or uploads from unexpected geographic locations
- Deploy endpoint detection and response (EDR) solutions like SentinelOne to detect post-exploitation activities following successful file uploads
Monitoring Recommendations
- Enable detailed logging for all API endpoint activities, particularly those involving file operations
- Set up alerting for any file execution events in the upload directories
- Monitor network traffic for command and control (C2) communications that may indicate successful exploitation
- Regularly audit uploaded files for signs of malicious content or web shells
How to Mitigate CVE-2026-6596
Immediate Actions Required
- Restrict network access to Langflow instances using firewall rules, allowing only trusted IP addresses
- Implement authentication requirements for file upload endpoints if not already enforced
- Review and remove any suspicious files that may have been uploaded to the system
- Consider temporarily disabling the file upload functionality until a patch is available
Patch Information
As of the last update on 2026-04-22, the vendor (langflow-ai) has not responded to disclosure attempts and no official patch has been released. Organizations should monitor the official Langflow repository and security channels for updates. Additional vulnerability context is available through VulDB CTI Report #358231 and VulDB Submission #791919.
Workarounds
- Deploy a reverse proxy or web application firewall (WAF) in front of Langflow to filter and validate file uploads before they reach the application
- Implement custom file validation logic at the network or application layer to restrict allowed file types and sizes
- Isolate Langflow instances in a sandboxed network segment to limit potential impact from successful exploitation
- Regularly scan uploaded files with antivirus and malware detection tools before processing
# Example: Restrict access to Langflow API using iptables
# Allow only trusted IP ranges to access the API endpoint
iptables -A INPUT -p tcp --dport 7860 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 7860 -s 192.168.0.0/16 -j ACCEPT
iptables -A INPUT -p tcp --dport 7860 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
