Critical CVSS 8.2 Actively exploited
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.
What this means
- Exposure
- Exploitable remotely over the network, without authentication and with no action from the victim.
- Impact
- An attacker can read sensitive data and alter some data.
- Weakness
- The authentication mechanism can be bypassed, letting an attacker pose as a legitimate user.
- Likelihood
- Exploitation is not hypothetical: CISA has observed it in the wild.
What to doTop priority: CISA sets the remediation deadline at 16 September 2026. Start with the instances exposed to the internet.
Read automatically from the CVSS vector, the weakness type (CWE) and the EPSS score. The technical description above remains the one published by NIST.