LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format. From version 1.74.2 to before version 1.83.7, 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. This issue has been patched in version 1.83.7.
Is CVE-2026-42271 exploited?
Listed in the CISA KEV catalog on 2026-06-08.
Federal remediation due 2026-06-22.
Past that date by 54 days.
EPSS puts exploitation in the next 30 days at 83%.
Public exploit code: none found in monitored sources.
Public detection rules exist.
Which products and versions are affected?
No affected package list recorded here yet.
Is there a patch?
No patch identifier recorded here yet.
What PlainSec published about CVE-2026-42271
PlainSec has not published a story about this CVE.