Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.0, Langflow is vulnerable to Path Traversal in the Knowledge Bases API (POST /api/v1/knowledge_bases). This occurs because user-supplied knowledge base names are used directly to create file paths without proper sanitization or containment checks. An authenticated attacker can exploit this flaw to create directories and write files anywhere on the server's filesystem. This vulnerability is fixed in 1.9.0.

Affected: PyPI: langflow

## Summary Langflow is vulnerable to Path Traversal in the Knowledge Bases API (`POST /api/v1/knowledge_bases`). This occurs because user-supplied knowledge base names are used directly to create file paths without proper sanitization or containment checks. An authenticated attacker can exploit this flaw to create directories and write files anywhere on the server's filesystem.

## Details The vulnerability exists in the `create_knowledge_base` function within `src/backend/base/langflow/api/v1/knowledge_bases.py`.

This function constructs file paths directly from the user-supplied `name` field without sanitization. The value is concatenated with the user's base directory and passed directly to `kb_path.mkdir()`. Immediately following the directory creation, the application writes `embedding_metadata.json` and `schema.json` into this attacker-controlled path.

## PoC (Proof of Concept) For the **Create** endpoint, an attacker can supply traversal sequences or absolute paths in the `name` field:

`../victim_user/evil_kb` or `/tmp/pwned`

This forces `kb_path.mkdir()` to create directories and write specific application files (`embedding_metadata.json` and `schema.json`) at any reachable path on the server.

## Impact Any Langflow instance exposing this endpoint to authenticated users is vulnerable. This exposes the server to: * **Cross-user data compromise:** Creation of directories and files within another tenant's knowledge base space. * **Arbitrary filesystem manipulation…

Affected: PyPI: langflow

## Summary Langflow is vulnerable to Path Traversal in the Knowledge Bases API (`POST /api/v1/knowledge_bases`). This occurs because user-supplied knowledge base names are used directly to create file paths without proper sanitization or containment checks. An authenticated attacker can exploit this flaw to create directories and write files anywhere on the server's filesystem.

## Details The vulnerability exists in the `create_knowledge_base` function within `src/backend/base/langflow/api/v1/knowledge_bases.py`.

This function constructs file paths directly from the user-supplied `name` field without sanitization. The value is concatenated with the user's base directory and passed directly to `kb_path.mkdir()`. Immediately following the directory creation, the application writes `embedding_metadata.json` and `schema.json` into this attacker-controlled path.

## PoC (Proof of Concept) For the **Create** endpoint, an attacker can supply traversal sequences or absolute paths in the `name` field:

`../victim_user/evil_kb` or `/tmp/pwned`

This forces `kb_path.mkdir()` to create directories and write specific application files (`embedding_metadata.json` and `schema.json`) at any reachable path on the server.

## Impact Any Langflow instance exposing this endpoint to authenticated users is vulnerable. This exposes the server to: * **Cross-user data compromise:** Creation of directories and files within another tenant's knowledge base space. * **Arbitrary filesystem manipulation…

Ein Angreifer kann mehrere Schwachstellen in Langflow ausnutzen, um Sicherheitsvorkehrungen zu umgehen, Daten zu manipulieren und vertrauliche Informationen offenzulegen.