High [CVE-2026-12773] BerriAI litellm: Improper authentication in MCP Proxy via UserAPIKeyAuth function
This high-severity Red Hat Linux advisory covers CVE-2026-12773 affecting Exploit Intelligence.
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Summary
A weakness has been identified in BerriAI litellm up to 1.59.8. Affected is the function UserAPIKeyAuth of the file litellm/proxy/_experimental/mcp_server/auth/user_api_key_auth_mcp.py of the component MCP Proxy.
Executing a manipulation can lead to improper authentication. The attack may be launched remotely.
The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure.
A flaw was found in BerriAI litellm, within its MCP Proxy component. A remote attacker could exploit an improper authentication vulnerability in the UserAPIKeyAuth function.
This could allow unauthorized access, potentially compromising the confidentiality, integrity, and availability of data within the system.
When the LiteLLM proxy MCP authentication flow mishandles 401/403 errors from API key validation, an attacker may bypass MCP proxy authentication and reach backend MCP servers that are configured with allow_all_keys: true. This issue affects litellm versions prior to 1.81.16 as shipped in select Red Hat products.
Red Hat severity: Important — CVSS 7.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L). Weakness: CWE-303.
Affected Red Hat products: Exploit Intelligence. Red Hat lists Red Hat Ansible Automation Platform 2; Red Hat OpenShift AI (RHOAI) as not affected.
Red Hat does not currently list a fixing RHSA for this CVE.
- 1.59.8
Official advisory · high-confidence parse· fetched 16 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 16 days ago·verify at source
Mitigation checklist
- Upgrade to litellm 1.81.16 or later. As a workaround, do not configure backend MCP servers with allow_all_keys: true, and restrict network access to the LiteLLM MCP proxy endpoints.
Official advisory · high-confidence parse· fetched 16 days ago·verify at source
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