Bug 2535604 (CVE-2026-59823)

Summary: CVE-2026-59823 litellm: LiteLLM: Server-Side Request Forgery via `user_config` parameter
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in LiteLLM, a proxy server for Large Language Model (LLM) APIs. An authenticated attacker with a valid virtual key can manipulate the `user_config` request parameter. This bypasses existing security checks, leading to Server-Side Request Forgery (SSRF). This vulnerability allows the attacker to force the server to make requests to internal or external resources, potentially exposing sensitive endpoints.
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Description OSIDB Bzimport 2026-09-16 18:52:13 UTC 
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.