Required actionApply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
KEV: BerriAI LiteLLM contains an improper authentication vulnerability in the MCP Streamable HTTP endpoint that could allow an unauthenticated attacker to establish an authenticated MCP session using an arbitrary Bearer token.
NVD: 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.
Hunt LiteLLM access logs for requests to /mcp/ endpoints with fabricated Bearer tokens. Proxy/WAF must capture Authorization headers — stock logs may not. Alert on /mcp/ access from external IPs.
PreconditionsNetwork reachability to LiteLLM MCP Streamable HTTP endpoint; no valid API key or credentials required; affects all versions prior to 1.84.0; the /mcp/ endpoint path must be exposed to the attacker (not blocked by proxy or gateway) agent
Exploit notesCVSS attack complexity: LOW | HIGH severity (CVSS 8.2). The attack is fully remote, requires no authentication, and involves sending any fabricated Bearer token in the Authorization header to the MCP endpoint. The OAuth2 passthrough fallback replaces failed validation with an empty UserAPIKeyAuth() object, granting access to all connected MCP tools and backend services.
SummaryCVE-2026-59822 is an authentication bypass in BerriAI LiteLLM's MCP Streamable HTTP endpoint. When LiteLLM key validation fails, an OAuth2 passthrough fallback path improperly substitutes an empty UserAPIKeyAuth() object instead of rejecting the request. An attacker can supply any fabricated Bearer token to bypass authentication and reach MCP tooling, potentially accessing upstream LLM API keys and backend service credentials. Fixed in version 1.84.0.
Tia coverage
First reported2026-07-29
First exploit report2026-09-30
Exploit report → KEV28 days after the listing
When Tia's reporting first covered this CVE and whether a report claimed exploitation before the KEV listing. Lead-time deltas are measured from the exploitation report only — plain coverage is not exploitation intel. See the story links under Mentioned in for coverage detail.