CVE-2026-59822

LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback

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

Weaknesses (CWE)

• CWE-287
• CWE-306

Advisories

• GHSA-7488-6r32-c95q — LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback
• PYSEC-2026-3479 — LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback

European references

• ENISA EUVD · EUVD-2026-42359
• GCVE · GCVE-0-2026-59822

Affected configurations (NVD CPE)

• cpe:2.3:a:litellm:litellm:*:*:*:*:*:*:*:* < 1.84.0

Affected products

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-honeypot
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-59822

Sources