CVE-2026-34046: Langflow: Authenticated Users Can Read, Modify, and Delete Any Flow via Missing Ownership Check

Vulnerability

IDOR in GET/PATCH/DELETE /api/v1/flow/{flowid}

The readflow helper in src/backend/base/langflow/api/v1/flows.py branched on the AUTOLOGIN setting to decide whether to filter by userid. When AUTOLOGIN was False (i.e., authentication was enabled), neither branch enforced an ownership check — the query returned any flow matching the given UUID regardless of who owned it.

This exposed any authenticated user to:

- Read any other user's flow, including embedded plaintext API keys - Modify the logic of another user's AI agents - Delete flows belonging to other users

The vulnerability was introduced by the conditional logic that was meant to accommodate public/example flows (those with userid = NULL) under auto-login mode, but inadvertently left the authenticated path without an ownership filter.

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Fix (PR #8956)

The fix removes the AUTOLOGIN conditional entirely and unconditionally scopes the query to the requesting user:

diff - authsettings = settingsservice.authsettings - stmt = select(Flow).where(Flow.id == flowid) - if authsettings.AUTOLOGIN: - stmt = stmt.where( - (Flow.userid == userid) | (Flow.userid == None) # noqa: E711 - ) + stmt = select(Flow).where(Flow.id == flowid).where(Flow.userid == userid)

All three operations — read, update, and delete — route through readflow, so the single change covers the full attack surface. A cross-user isolation test (testreadflowsuserisolation) was added to prevent regression.

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Acknowledgements

Langflow thanks the security researcher who responsibly disclosed this vulnerability:

- @chximn-dt