Vulnerability Report

CVE-2026-42271

RCE CISA KEV Active

Title: Authenticated Remote Code Execution in MCP Server Endpoints

RCE

Proof Of Concept

PoC Available for CVE-2026-42271

CWE Category CWE-77

Published Date May 08, 2026

Modified Date Jun 09, 2026

Exploit Status Available

Score 8.7 CVSS v4.0

Exploit Probability (EPSS)

53.70%

Vulnerability Summary

CVE-2026-42271: 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.

Impacted Vendors

litellm 1

Reference Links

https://github.com/BerriAI/litellm/releases/tag/v1.83.7-stable https://github.com/BerriAI/litellm/security/advisories/GHSA-v4p8-mg3p-g94g

CVSS v4.0

Source Entity [email protected]

Severity HIGH

8.7

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

N/A

RAW VECTOR

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS v3.1