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CVE-2026-59822

HIGH severity · CVSS 8.2 · Improper authentication · actively exploited (CISA KEV)
8.2CVSS HIGH exploited
Actively exploited in the wild (CISA Known Exploited Vulnerabilities). Added to KEV 2026-09-02. US federal agencies must patch by 2026-09-16.

Summary

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.

Impact & exploitability

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
Confidentiality impactHigh
Integrity impactLow
Availability impactNone
Exploit probability (EPSS)1%

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Affected products we track (1)

LiteLLM

Recommendation

This vulnerability is being actively exploited in the wild — patch affected products urgently. Open any affected product above for its exact safe version.

Official patch: https://github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2c ↗

Additional information