Authentication Bypass by Spoofing in Langflow - #VU142385
Published: August 13, 2026
Vulnerability details
The vulnerability allows a remote user to overwrite MCP client configuration files on the server and bypass a local-only access restriction.
The vulnerability exists due to authentication bypass by spoofing in the MCP configuration installation endpoint (`POST /api/v1/mcp/project/{project_id}/install`) and `get_client_ip` helper when handling requests with a spoofed `X-Forwarded-For` header. A remote user can send a specially crafted request with `X-Forwarded-For: 127.0.0.1` to overwrite MCP client configuration files on the server and bypass a local-only access restriction.
The write target is limited to a fixed set of per-OS developer tool configuration files resolved by the application rather than an attacker-supplied arbitrary path.