CVE-2026-12773: BerriAI litellm MCP Proxy user_api_key_auth_mcp.py UserAPIKeyAuth improper authentication

Description

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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack vector

Network

Complexity

Low

Privileges

None

User interaction

None

Confidentiality

High

Integrity

High

Availability

High

Scope

Unchanged

Exploitation

Is it being used?

Exploit prediction (EPSS)1.0% · higher than 63% of CVEs

Exploited in the wildNo evidence yet

CISA KEVNot listed

Ransomware campaign useNot known

Affected products

Which versions

LI

litellm · BerriAI

1.59.0; 1.59.1; 1.59.2; 1.59.3; 1.59.4; 1.59.5; +3 more · source: vendor, NVD

EI

Exploit Intelligence · Red Hat

All versions, or not specified · source: CISA