CVE-2026-42271
LiteLLM: Authenticated command execution via MCP stdio test endpoints
Description
### Impact Two endpoints used to preview an MCP server before saving it — `POST /mcp-rest/test/connection` and `POST /mcp-rest/test/tools/list` — accepted a full server configuration in the request body, including the `command`, `args`, and `env` fields used by the stdio transport. When called with a stdio configuration, the endpoints attempted to connect, which spawned the supplied command as a subprocess on the proxy host with the privileges of the proxy process. The endpoints were gated only by a valid proxy API key, with no role check. Any authenticated user — including holders of low-privilege internal-user keys — could therefore run arbitrary commands on the host. ### Patches Fixed in **`1.83.7`**. Both test endpoints now require the `PROXY_ADMIN` role, bringing them into line with the save endpoint. ### Workarounds If upgrading is not immediately possible, developers should block `POST /mcp-rest/test/connection` and `POST /mcp-rest/test/tools/list` at their reverse proxy or API gateway.
How to fix CVE-2026-42271
To remediate CVE-2026-42271, upgrade the affected package to a fixed version below.
- —upgrade to 1.83.7 or later
Is CVE-2026-42271 being exploited?
Yes — CVE-2026-42271 is on the CISA Known Exploited Vulnerabilities (KEV) catalog. Patch immediately.
Affected packages (1)
- >= 1.74.2, < 1.83.7
CVSS scores
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