- High 8.8
- Known exploited (CISA KEV)
CVE-2026-59822
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
The facts
- Published
- 8 July 2026
- Last changed
- 3 September 2026
- NVD status
- Analyzed
- Severity
- High, CVSS 8.8 out of 10 (version 4.0)
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R… - Weakness
- Affects
- litellm litellm
- Known exploited
- Yes. CISA added it to the Known Exploited Vulnerabilities catalogue on 2 September 2026.
- EPSS
- 0.8% chance of exploitation activity in the next 30 days (percentile 57).
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