GET/PATCH/DELETE /api/v1/flow/{flow_id}The _read_flow helper in src/backend/base/langflow/api/v1/flows.py branched on the AUTO_LOGIN setting to decide whether to filter by user_id. When AUTO_LOGIN 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:
The vulnerability was introduced by the conditional logic that was meant to accommodate public/example flows (those with user_id = NULL) under auto-login mode, but inadvertently left the authenticated path without an ownership filter.
The fix removes the AUTO_LOGIN conditional entirely and unconditionally scopes the query to the requesting user:
- auth_settings = settings_service.auth_settings
- stmt = select(Flow).where(Flow.id == flow_id)
- if auth_settings.AUTO_LOGIN:
- stmt = stmt.where(
- (Flow.user_id == user_id) | (Flow.user_id == None) # noqa: E711
- )
+ stmt = select(Flow).where(Flow.id == flow_id).where(Flow.user_id == user_id)
All three operations — read, update, and delete — route through _read_flow, so the single change covers the full attack surface. A cross-user isolation test (test_read_flows_user_isolation) was added to prevent regression.
Langflow thanks the security researcher who responsibly disclosed this vulnerability:
{
"cwe_ids": [
"CWE-639",
"CWE-862"
],
"severity": "HIGH",
"github_reviewed": true,
"nvd_published_at": "2026-03-27T21:17:27Z",
"github_reviewed_at": "2026-03-27T19:36:23Z"
}