CVE-2026-59823

LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format. Prior to 1.83.9, an authenticated LiteLLM Proxy caller with a valid virtual key can place api_base inside the user_config request body to bypass is_request_body_safe, which blocks top-level api_base and base_url but previously did not inspect or reject user_config. Because user_config constructs the outbound router, the nested destination redirects a server-side request to an internal or external host selected by the caller and can expose endpoints the caller cannot otherwise access. This issue is fixed in version 1.83.9.

• https://github.com/BerriAI/litellm/commit/47214be317f45a2d2ac08258362e0481411eb427
• https://github.com/BerriAI/litellm/pull/25827
• https://github.com/BerriAI/litellm/security/advisories/GHSA-hx8v-g79f-8w5f