CVE-2026-42271

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.

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.

Untrusted input is inserted into a command that is later executed by the application, allowing the attacker to alter the intent of that command. Typical impact: arbitrary command execution in the application's environment.

CVE-2026-42271 has a CVSS score of 8.8 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.83.7); upgrading removes the vulnerable code path.

Kodem intelligence

Fixed in 1.83.7. Both test endpoints now require the PROXY_ADMIN role, bringing them into line with the save endpoint.

1. What is CVE-2026-42271? CVE-2026-42271 is a high-severity command injection vulnerability in litellm (pip), affecting versions >= 1.74.2, < 1.83.7. It is fixed in 1.83.7. Untrusted input is inserted into a command that is later executed by the application, allowing the attacker to alter the intent of that command.
2. How severe is CVE-2026-42271? CVE-2026-42271 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of litellm are affected by CVE-2026-42271? litellm (pip) versions >= 1.74.2, < 1.83.7 is affected.
4. Is there a fix for CVE-2026-42271? Yes. CVE-2026-42271 is fixed in 1.83.7. Upgrade to this version or later.
5. Is CVE-2026-42271 exploitable, and should I be worried? Whether CVE-2026-42271 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-42271 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-42271? Upgrade litellm to 1.83.7 or later.