CVE-2026-42271
BerriAI LiteLLM Command Injection Vulnerability
BerriAI LiteLLM
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.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 8 June 2026. US federal agencies were required to remediate it by 22 June 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 83%, which is higher than 99.6% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Frequently asked questions
Is CVE-2026-42271 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2026-42271.
What does CVE-2026-42271 affect?
CVE-2026-42271 affects BerriAI LiteLLM. 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.
How severe is CVE-2026-42271?
CVE-2026-42271 is rated HIGH with a CVSS base score of 8.8. EPSS puts the probability of exploitation in the next 30 days at 83%, higher than 99.6% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 22 June 2026.
How should organisations respond to CVE-2026-42271?
Apply the vendor patch for BerriAI LiteLLM as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.