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LitellmApplication

CVE-2026-12773

CRITICAL · 9.8 CVSS v3.1 Published 2026-06-21
Fix available
A fix is available. Upgrade to 1.59.9 or later.
See remediation →
100/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A critical authentication bypass vulnerability exists in the UserAPIKeyAuth function within litellm's MCP Proxy experimental component (litellm/proxy/_experimental/mcp_server/auth/user_api_key_auth_mcp.py). The weakness allows remote attackers to bypass proper API key authentication, potentially gaining unauthorized access to the proxy service.

MitigationUpgrade litellm beyond version 1.59.8 when a patched version becomes available. Until then, consider disabling the experimental MCP Proxy or implementing additional authentication layers such as network segmentation, VPN access, or external auth gateways.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
LitellmApplication
Affected:< 1.59.9

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify litellm installation and version
    Run 'pip show litellm' or check your package manager to find the installed version of litellm
    Affected if The installed version is below 1.59.9 (e.g., 1.59.8, 1.59.7, etc.)
  2. Determine if MCP Proxy component is in use
    Search your codebase or deployment for references to 'mcp_server' or the path 'litellm/proxy/_experimental/mcp_server/' - check for any MCP Proxy configuration files or enabled features
    Affected if MCP Proxy component is enabled or deployed in your environment
  3. Locate the vulnerable auth module
    Check for the presence of the file 'user_api_key_auth_mcp.py' within the litellm installation at 'litellm/proxy/_experimental/mcp_server/auth/'
    Affected if The file exists in your litellm installation and is being used for authentication
  4. Verify MCP authentication configuration
    Review your litellm configuration or environment variables for any MCP-related auth settings, specifically any use of UserAPIKeyAuth for MCP endpoints
    Affected if UserAPIKeyAuth is configured for MCP Proxy endpoints

You are affected if litellm version is below 1.59.9 AND the MCP Proxy component with the vulnerable UserAPIKeyAuth function is enabled and accessible in your environment.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.59.9 or later
Fixed in 1.59.9
Interim mitigation

Upgrade litellm beyond version 1.59.8 when a patched version becomes available. Until then, consider disabling the experimental MCP Proxy or implementing additional authentication layers such as network segmentation, VPN access, or external auth gateways.

Recommended fix High confidence

1.59.9

  1. Identify the current litellm version in use (e.g., pip show litellm or check requirements.txt)
  2. Upgrade litellm to version 1.59.9 or later using: pip install litellm>=1.59.9
  3. Verify the upgrade was successful by checking the installed version
  4. Restart any litellm services to load the patched version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Litellm Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-12773 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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