Vulnerabilities

BerriAI LiteLLM, a widely used self-hosted AI gateway and proxy server for calling LLM APIs, fails to properly authenticate requests to its MCP Streamable HTTP endpoint in versions prior to 1.84.0. An unauthenticated attacker can send a fabricated Authorization header that triggers an OAuth2 passthrough fallback, which replaces failed LiteLLM key validation with an empty UserAPIKeyAuth() object and lets the request reach MCP tooling without any valid LiteLLM key. Successful exploitation grants unauthenticated access to the gateway's MCP tooling with high confidentiality impact per the CVSS 4.0 score of 8.8, and public reporting describes attackers chaining LiteLLM weaknesses from authentication bypass to root code execution and cloud credential theft. Any organization running LiteLLM before 1.84.0 is affected, particularly gateways exposed to the internet. The flaw is confirmed exploited in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2026-09-02, while EPSS currently estimates a 0.9% probability of exploitation in the next 30 days.

Do: Upgrade LiteLLM to version 1.84.0 or later immediately, in line with the CISA KEV required action and BOD 26-04 guidance for internet-exposed assets. Audit whether the MCP endpoint is reachable from the internet and check for signs of exploitation, including unexpected MCP tool calls, use of fabricated Authorization headers, and use of default or example admin keys such as 'sk-1234'. Until patched, restrict access to the MCP endpoint and review cloud credentials accessible from the gateway host for signs of theft or root-level activity.

LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format. Prior to 1.83.7-stable, LiteLLM Skills archive extraction did not sufficiently validate file paths from uploaded skill ZIP archives, allowing an authenticated user with access to LiteLLM LLM API routes or a key whose allowed_routes includes /v1/skills, anthropic_routes, or llm_api_routes to upload a crafted skill archive containing path traversal entries that could be written outside the intended extraction or staging directory. This issue is fixed in version 1.83.7-stable.

LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format. Prior to 1.84.0, a Host-header parsing flaw in the LiteLLM proxy could, under specific conditions, allow unauthenticated access to protected management routes. The auth layer derived the effective route from request.url.path in litellm/proxy/auth/auth_utils.py::get_request_route(), which Starlette reconstructs from the Host header. A crafted Host could therefore make the auth gate evaluate a different route from the one FastAPI dispatched. This vulnerability is fixed in 1.84.0.

A weakness has been identified in BerriAI litellm up to 1.59.8. Affected is the function UserAPIKeyAuth of the file litellm/proxy/_experimental/mcp_server/auth/user_api_key_auth_mcp.py of the component MCP Proxy. Executing a manipulation can lead to improper authentication. The attack may be launched remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure.