{"id":"GHSA-4hf8-5mjm-rfgq","summary":"Streamable HTTP mode exposes LINE Desktop read/send tools without MCP authentication","details":"# Streamable HTTP mode exposes LINE Desktop read/send tools without MCP authentication\n\n## Summary\n\n`line-desktop-mcp` supports a `--http-mode` Streamable HTTP transport for use with clients such as n8n. In this mode the server binds to `0.0.0.0` and exposes the MCP `/mcp` endpoint without an MCP-layer authentication check. Any network client that can reach the port can initialize a session, list tools, and call tools that read LINE Desktop chat history or send LINE messages through the already logged-in desktop application.\n\nThis is High for deployments where the HTTP port is reachable beyond the local host, because the server acts with the user authority of the logged-in LINE Desktop session. It is lower if the listener is strictly firewalled to trusted local clients.\n\n## Affected version\n\nRepository: `dtwang/line-desktop-mcp`\n\nCurrent source checked: `fbed0d2d3048e63f48a356a1267ed8ec5e78f3ae` on `main`, committed 2026-05-14.\n\nPublished npm package checked: `line-desktop-mcp@1.1.1`.\n\n## Source evidence\n\n`README.md` documents Streamable HTTP mode:\n\n```text\nnpx line-desktop-mcp@latest --http-mode --port 3000\n```\n\nThe same README documents MCP endpoints at `/mcp` and explains that this mode is intended for clients such as n8n.\n\n`src/server.js` registers LINE Desktop tools including:\n\n- `get_line_chatroom_history_default`\n- `get_line_chatroom_history_long`\n- `get_line_chatroom_history_short`\n- `send_message_manual`\n- `send_message_auto`\n\nThose tool handlers call into the desktop automation layer: `getChatHistory(...)` and `sendChatMessage(...)`.\n\nIn HTTP mode, `src/server.js` creates an Express app and Streamable HTTP transport, accepts POSTs to `/mcp`, creates sessions, connects the transport to the MCP server, and calls `transport.handleRequest(...)`. I did not find an authentication or bearer-token check before session creation or tool invocation.\n\nThe listener is explicitly network-bound:\n\n```js\napp.listen(port, 0.0.0.0, () =\u003e {\n  console.error(`LINE Desktop MCP Server running on Streamable HTTP mode`);\n  console.error(`  Local:   http://127.0.0.1:${port}${endpoint}`);\n  console.error(`  Network: http://0.0.0.0:${port}${endpoint}`);\n});\n```\n\n## Vulnerability chain\n\n1. A user starts the server with `--http-mode --port 3000`.\n2. The server binds on `0.0.0.0:3000`, not only loopback.\n3. A network client reaches `/mcp` and sends the normal MCP initialize request.\n4. The server creates a Streamable HTTP session without authenticating the caller.\n5. The caller can list and invoke LINE Desktop tools.\n6. Tool calls execute through the logged-in LINE Desktop application on the user workstation.\n\n## Impact\n\nAn unauthenticated network client can read LINE chat history through the MCP history tools and can send LINE messages through the send-message tools, including `send_message_auto` when the tool call requests immediate sending. The attacker does not need LINE credentials or a LINE API token; they only need network reachability to the MCP HTTP port.\n\nThe practical impact is disclosure of private LINE conversations and unauthorized messages sent as the logged-in desktop user.\n\n## Suggested fix\n\nRequire authentication before accepting Streamable HTTP MCP sessions or tool calls. For example:\n\n- require a bearer token or local secret when `--http-mode` is used;\n- bind HTTP mode to `127.0.0.1` by default unless the operator explicitly opts into network exposure;\n- refuse to start `0.0.0.0` HTTP mode without authentication;\n- document that `host.docker.internal` / n8n setups must still authenticate to the MCP server.\n\nA defense-in-depth improvement would also keep `send_message_auto` disabled unless explicitly enabled by a server-side flag, because it converts MCP tool access into immediate message sending as the desktop user.","aliases":["CVE-2026-49357"],"modified":"2026-06-26T22:11:30.924727Z","published":"2026-06-26T21:50:49Z","database_specific":{"github_reviewed_at":"2026-06-26T21:50:49Z","nvd_published_at":"2026-06-19T14:16:23Z","cwe_ids":["CWE-306","CWE-862"],"severity":"HIGH","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/dtwang/line-desktop-mcp/security/advisories/GHSA-4hf8-5mjm-rfgq"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49357"},{"type":"WEB","url":"https://github.com/dtwang/line-desktop-mcp/commit/680617894981ea93f8f6ceb51ecde7519754d501"},{"type":"PACKAGE","url":"https://github.com/dtwang/line-desktop-mcp"}],"affected":[{"package":{"name":"line-desktop-mcp","ecosystem":"npm","purl":"pkg:npm/line-desktop-mcp"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.1.2"}]}],"database_specific":{"last_known_affected_version_range":"\u003c= 1.1.1","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-4hf8-5mjm-rfgq/GHSA-4hf8-5mjm-rfgq.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N"}]}