High severityNVD Advisory· Published Jul 8, 2026· Updated Jul 9, 2026
LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback
CVE-2026-59822
Description
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.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
litellmPyPI | < 1.84.0 | 1.84.0 |
Affected products
1Patches
Vulnerability mechanics
References
6- github.com/advisories/GHSA-7488-6r32-c95qghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-59822ghsaADVISORY
- github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2cghsax_refsource_MISCWEB
- github.com/BerriAI/litellm/pull/26463ghsax_refsource_MISCWEB
- github.com/BerriAI/litellm/releases/tag/v1.84.0ghsax_refsource_MISCWEB
- github.com/BerriAI/litellm/security/advisories/GHSA-7488-6r32-c95qghsax_refsource_CONFIRMWEB
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