CVE-2026-59822
LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback
- State
- Published
- Severity
- 8.8 High
- Published
- Jul 8, 2026
- Updated
- Sep 3, 2026
- Reserved
- Jul 7, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.8 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N | GitHub_M |
Weaknesses
Affected Products
| Product | Versions |
|---|---|
litellmBerriAI |
|
References
- https://github.com/BerriAI/litellm/security/advisories/GHSA-7488-6r32-c95q
- https://github.com/BerriAI/litellm/pull/26463
- https://github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2c
- https://github.com/BerriAI/litellm/releases/tag/v1.84.0
- https://www.wiz.io/blog/ai-infrastructure-honeypotthird-party-advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-59822government-resource
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