CVE-2026-6596: Langflow unrestricted file upload in API Endpoint

Executive brief

Langflow is a tool used to build and manage AI-driven applications. A security flaw in its file upload system allows an attacker to upload files of any size without needing to log in. This can be used to fill up server storage or consume system resources, potentially causing the service to crash or become unavailable to legitimate users.

Technical details

A vulnerability exists in the `create_upload_file` function within `src/backend/base/Langflow/api/v1/endpoints.py` of Langflow. The endpoint lacks proper authentication and fails to enforce file size restrictions on uploaded content. A remote, unauthenticated attacker can exploit this by sending large volumes of data or excessively large files to the API, leading to resource exhaustion (disk space or memory) and a Denial of Service. While the vendor was reportedly unresponsive during initial disclosure, patches are available in version 0.9.1 for langflow-base.

Affected products

• langflow-ai langflow-base < 0.9.1
• langflow-ai langflow <= 1.1.0

Timeline

• 2026-04-20: disclosed
• 2026-04-20: advisory

References

• https://api.github.com/users/ventusfortis
• https://github.com/ventusfortis
• https://api.github.com/users/ventusfortis/gists%7B/gist_id%7D
• https://api.github.com/users/ventusfortis/repos
• https://avatars.githubusercontent.com/u/71601301?v=4
• https://api.github.com/users/ventusfortis/events%7B/privacy%7D