CVE-2026-59822

UNKNOWN 0.0

⚠️ CISA KEV

LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback

CVSS Score

0.0

EPSS Score

0.5%

EPSS Percentile

42th

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.

CWE	CWE-287 CWE-306
Vendor	berriai
Product	litellm
Published	Jul 8, 2026
Last Updated	Sep 3, 2026

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Affected Versions

BerriAI / litellm

< 1.84.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/BerriAI/litellm/security/advisories/GHSA-7488-6r32-c95q github.com: https://github.com/BerriAI/litellm/pull/26463 github.com: https://github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2c github.com: https://github.com/BerriAI/litellm/releases/tag/v1.84.0 wiz.io: https://www.wiz.io/blog/ai-infrastructure-honeypot cisa.gov: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-59822