BerriAI litellm up to 1.59.8 MCP Proxy user_api_key_auth_mcp.py UserAPIKeyAuth improper authentication

Summaryinfo

A vulnerability has been found in BerriAI litellm up to 1.59.8 and classified as critical. Affected by this vulnerability is the function UserAPIKeyAuth of the file litellm/proxy/_experimental/mcp_server/auth/user_api_key_auth_mcp.py of the component MCP Proxy. The manipulation leads to improper authentication. This vulnerability is referenced as CVE-2026-12773. Remote exploitation of the attack is possible. Furthermore, an exploit is available. The vendor was contacted early about this disclosure.

Detailsinfo

A vulnerability was found in BerriAI litellm up to 1.59.8 and classified as critical. This issue affects the function UserAPIKeyAuth of the file litellm/proxy/_experimental/mcp_server/auth/user_api_key_auth_mcp.py of the component MCP Proxy. The manipulation with an unknown input leads to a improper authentication vulnerability. Using CWE to declare the problem leads to CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Impacted is confidentiality, integrity, and availability.

It is possible to read the advisory at gist.github.com. The identification of this vulnerability is CVE-2026-12773. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details as well as a public exploit are known.

The exploit is available at gist.github.com. It is declared as proof-of-concept. The vendor was contacted early about this disclosure.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-38139). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• BerriAI

Name

• litellm

Version

• 1.59.0
• 1.59.1
• 1.59.2
• 1.59.3
• 1.59.4
• 1.59.5
• 1.59.6
• 1.59.7
• 1.59.8

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

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Exploitinginfo

Threat Intelligenceinfo

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Timelineinfo

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Entryinfo

Submitinfo

Accepted

• Submit #811282: litellm <= 1.59.8 Improper Authentication (CWE-287) (by Eric-c)

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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