CVE-2026-12773 BerriAI litellm MCP Proxy user_api_key_auth_mcp.py UserAPIKeyAuth improper authentication
Remote attackers can bypass authentication in the LiteLLM MCP Proxy component, gaining unauthorized access to protected resources.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-12773?
CVE-2026-12773 is a medium-severity authentication bypass vulnerability in BerriAI litellm, published on 21 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-12773?
3 open source packages ship an affected version, including litellm. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
litellm PyPI | All versions | 1.84.0 |
litellm PyPI | All versions | 1.84.0 |
litellm PyPI | All versions | 1.84.0 |
Products include Litellm Litellm.
How do I fix CVE-2026-12773?
Upgrade litellm to 1.84.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-12773 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-12773 exists.
Other vulnerabilities in BerriAI litellm
Sources
Also known as ECHO-ec81-be0d-b655, GHSA-4jcj-7x88-m979, MINI-4mq8-j5px-v3wj, MINI-972q-gh6p-7f99, PYSEC-2026-4067.