CVE-2026-59822

HIGH8.8

LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback

Published Jul 8, 2026

Modified 6 days ago

Details

LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format. Prior to 1.84.0, LiteLLM's MCP Streamable HTTP endpoint allowed an unauthenticated attacker to use a fabricated Authorization header to trigger an OAuth2 passthrough fallback path that replaced failed LiteLLM key validation with an empty UserAPIKeyAuth() object, allowing requests to reach MCP tooling without a valid LiteLLM key. This issue is fixed in version 1.84.0.

References

WEB

https://github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2c

WEB

https://github.com/BerriAI/litellm/pull/26463

WEB

https://github.com/BerriAI/litellm/releases/tag/v1.84.0

WEB

https://github.com/BerriAI/litellm/security/advisories/GHSA-7488-6r32-c95q

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2026-59822

CVSS Analysis