GitHub Advisoryadvisory · PyPI

GHSA-7488-6r32-c95q LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback

HIGH Published 2026-07-22 Modified 2026-07-22 Official page ↗
Aliases
CVE-2026-59822
Ecosystem
PyPI
Packages
litellm
Severity
High
CVSS vector
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
Weaknesses
CWE-287
Reviewed
2026-07-22

Affected packages

• PyPI litellm: < 1.84.0 → fixed in 1.84.0

Description

Impact LiteLLM's MCP Streamable HTTP endpoint could allow an unauthenticated attacker to establish an authenticated MCP session using an arbitrary Bearer token. The MCP auth handler supported OAuth2 passthrough for upstream MCP servers, but the fallback path could replace failed LiteLLM key validation with an empty `UserAPIKeyAuth()` object. This allowed requests with a fabricated `Authorization` header to reach MCP tooling without a valid LiteLLM key. An attacker could use this to list and call configured MCP tools and access connected services exposed through MCP. Patches The issue is fixed in `1.84.0`. We recommend upgrading to `1.84.0` or later. Workarounds If upgrading is not immediately possible, disable MCP routes or block access to `/mcp/` and related MCP endpoints at your reverse proxy or API gateway. References • v1.84.0

Related

Alias · CVE (1)

  • CVE-2026-59822 LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format. vulnerability

Weakness · CWE (1)

  • CWE-287 Improper Authentication weakness

References