Summary Multiple critical API endpoints in Langflow are missing authentication controls, allowing any unauthenticated user to access sensitive user conversation data, transaction histories, and perform destructive operations including message deletion. This affects endpoints handling personal data and system operations that should require proper authorization.

Details The vulnerability exists in three API endpoints within src/backend/base/langflow/api/v1/monitor.py that are missing the required dependencies=[Depends(getcurrentactiveuser)] authentication dependency:

Affected Endpoints:

1. GET /api/v1/monitor/messages (Line 61) python @router.get("/messages") # ❌ Missing authentication async def getmessages( session: DbSession, flowid: Annotated[UUID | None, Query()] = None, sessionid: Annotated[str | None, Query()] = None, # ... other parameters ) -> list[MessageResponse]:

2. GET /api/v1/monitor/transactions (Line 183) python @router.get("/transactions") # ❌ Missing authentication async def gettransactions( flowid: Annotated[UUID, Query()], session: DbSession, params: Annotated[Params | None, Depends(customparams)], ) -> Page[TransactionTable]:

3. DELETE /api/v1/monitor/messages/session/{sessionid} (Line 165) python @router.delete("/messages/session/{sessionid}", statuscode=204) # ❌ Missing authentication async def deletemessagessession( sessionid: str, session: DbSession, ):

Inconsistency Evidence: Other endpoints in the same file properly implement authentication: python @router.get("/messages/sessions", dependencies=[Depends(getcurrentactiveuser)]) # ✅ Properly secured @router.delete("/messages", statuscode=204, dependencies=[Depends(getcurrentactiveuser)]) # ✅ Properly secured

PoC Complete reproduction steps to demonstrate the vulnerability:

Prerequisites: 1. Start a Langflow server instance 2. Ensure no authentication headers or API keys are provided

Reproduction Commands: bash 1. Access all user conversations without authentication curl http://localhost:7860/api/v1/monitor/messages

2. Access transaction history without authentication curl "http://localhost:7860/api/v1/monitor/transactions?flowid=00000000-0000-0000-0000-000000000000"

3. Delete user messages by session without authentication curl -X DELETE http://localhost:7860/api/v1/monitor/messages/session/00000000-0000-0000-0000-000000000000

Expected vs Actual Behavior: - Expected: All requests should return 401 Unauthorized - Actual: All requests return successful responses with sensitive data or perform destructive operations

Impact

Vulnerability Type: Broken Authentication and Authorization (OWASP Top 10 - A01:2021)

Severity: High

Who is Impacted: - All Langflow users: Personal conversation data exposed to unauthorized access - System administrators: Transaction logs disclosed

Specific Impacts: 1. Data Breach: Unauthorized access to user conversations containing potentially sensitive personal information 2. Privacy Violation: Transaction histories and user activity patterns exposed without consent 3. Data Destruction: Malicious actors can delete user conversation histories without authorization 4. Compliance Risk: Potential violations of data protection regulations (GDPR, CCPA, etc.) 5. System Intelligence: Attackers can gather information about system usage patterns and user behavior

Attack Scenarios: - Malicious users accessing proprietary conversation data - Malicious users deleting other users' conversation histories - Automated scraping of all user conversations for data harvesting - Reconnaissance attacks to understand system architecture and usage patterns

Recommended Fix: Add authentication dependencies to all affected endpoints:

python @router.get("/messages", dependencies=[Depends(getcurrentactiveuser)]) @router.get("/transactions", dependencies=[Depends(getcurrentactiveuser)]) @router.delete("/messages/session/{sessionid}", dependencies=[Depends(getcurrentactiveuser)])

Environment: - Langflow Version: Current main branch - Affected Components: API v1 monitoring endpoints - Authentication System: FastAPI dependency injection with getcurrentactiveuser

<img width="1908" height="1029" alt="25-090901" src="https://github.com/user-attachments/assets/44bd03b4-6ada-45b7-b81b-9cb83747172b" />

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.