CVE-2026-55450 — Langflow: Unauthenticated file upload leads to DoS (space exhaustion) and information leak

Affected: langflow-ai langflow

Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.1, unauthenticated users can upload any amount of data to the server without any limitations. No need for any prior knowledge, only network access to Langflow. This can lead to space exhaustion on the server. In addition, in the response, the absolute path of the uploaded file is reported to the attacker, which is an information leak that can assist in chaining other primitives. This vulnerability is fixed in 1.9.1.

GHSA-x223-p2gf-v735 — Langflow: Unauthenticated file upload leads to DoS (space exhaustion) and information leak

Affected: PyPI: langflow

### Summary Unauthenticated users can upload any amount of data to the server without any limitations. No need for any prior knowledge, only network access to Langflow.

This can lead to space exhaustion on the server.

In adition, in the response, the absolute path of the uploaded file is reported to the attacker, which is an information leak that can assist in chaining other primitives.

Tested on commit 2d67402b1dbaefcbce85a244d4a6cd5e4bda1cfe

### Details Code is in `langflow/api/v1/[endpoints.py](http://endpoints.py/)`: ```python @router.post( "/upload/{flow_id}", status_code=HTTPStatus.CREATED, deprecated=True, ) async def create_upload_file( file: UploadFile, flow_id: UUID, ) -> UploadFileResponse: ... ``` As can be seen above, there is no authentication. There is not validation over `flow_id` as well, unlike other endpoints: ``` flow_id_str = str(flow_id) file_path = await asyncio.to_thread(save_uploaded_file, file, folder_name=flow_id_str) ``` Function `save_uploaded_file` saves the file to local file-system. Suggested fix: 1. Add authentication to route. 2. Only return relative path or filename.

### PoC PoC: ```bash curl 'http://localhost:7860/api/v1/upload/<any_uuid>' -F "file=@<any_file>" ```

Example: ```bash # curl 'http://localhost:7860/api/v1/upload/11111111-1111-1111-1111-111111111111' -F "file=@/tmp/dummy.txt" {"flowId":"11111111-1111-1111-1111-111111111111","file_path":"/Users/ori/Library/Caches/langflow/11111111-1111-1…

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CVE-2026-55450 — Langflow: Unauthenticated file upload leads to DoS (space exhaustion) and information leak

GHSA-x223-p2gf-v735 — Langflow: Unauthenticated file upload leads to DoS (space exhaustion) and information leak