CVE-2026-12773: LiteLLM MCP Proxy Has Improper Authentication Vulnerability

MODERATE
Advisory Identifier: GHSA-4jcj-7x88-m979
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CVSS 7.3
CWE-287 CWE-303
Published
Advisory Summary

CVE-2026-12773 is a MODERATE (CVSS 7.3) mcp proxy has improper authentication vulnerability (CWE-287: Improper Authentication) affecting LiteLLM libraries in the PyPI ecosystem. The issue involves mcp proxy has improper authentication. Remediation is available by upgrading affected packages to version 1.84.0.

CVE-2026-12773 at a Glance

CVE Identifier CVE-2026-12773
GHSA Identifier GHSA-4jcj-7x88-m979
Severity MODERATE
CVSS v3.1 Base Score 7.3
CWE Classification CWE-287: Improper Authentication
Affected Product LiteLLM
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-12773

To remediate this vulnerability, upgrade all affected LiteLLM dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

litellm fixed: 1.84.0 
pip install litellm>=1.84.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show litellm

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-12773, inspect your installed packages using pip:

pip show litellm

Analyze the terminal output to locate any version of LiteLLM in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.84.0), your application is affected.

Note: The pip show litellm command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-287: Improper Authentication, where when an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. In LiteLLM, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

CVE-2026-12773 Affected LiteLLM Versions

1 component(s)
Fixed Versions:
1.84.0
Product / Package Ecosystem Affected Versions Fixed Version
litellm
pypi/litellm
PyPI
< 1.84.0
1.84.0

References

LiteLLM Source Repository REPOSITORY
https://github.com/BerriAI/litellm
LiteLLM Security Information SECURITY
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12773.json
vuldb.com/cve/cve-2026-12773 WEB
https://vuldb.com/cve/CVE-2026-12773
vuldb.com/submit/811282 WEB
https://vuldb.com/submit/811282
vuldb.com/vuln/372515 WEB
https://vuldb.com/vuln/372515
vuldb.com/vuln/372515/cti WEB
https://vuldb.com/vuln/372515/cti
NVD — CVE-2026-12773 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-12773
Security Fix Commit FIX COMMIT
https://github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2c
LiteLLM Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-12773
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2491112
LiteLLM Source Repository REPOSITORY
https://gist.github.com/YLChen-007/3cfaad10a69d7a15e4d4d458cb53309e

Frequently Asked Questions

What is CVE-2026-12773?
CVE-2026-12773 is a security vulnerability in LiteLLM involving MCP Proxy Has Improper Authentication under CWE-287: Improper Authentication.
Which LiteLLM versions are affected?
Affected versions include releases prior to 1.84.0 across affected packages: litellm.
What version fixes CVE-2026-12773?
Upgrading to 1.84.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is litellm affected?
Yes, litellm is affected in releases prior to 1.84.0. Upgrade your dependency to 1.84.0 or later.
What is the CVSS score of CVE-2026-12773?
CVE-2026-12773 has a CVSS v3.1 base score of 7.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.
What CWE is associated with CVE-2026-12773?
CVE-2026-12773 is classified under CWE-287: Improper Authentication (When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.).
How can I check PyPI dependencies for CVE-2026-12773?
Run the dependency tree command: 'pip show litellm'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4jcj-7x88-m979",
  "modified" : "2026-09-10T22:32:02Z",
  "published" : "2026-06-21T06:32:07Z",
  "aliases" : [ "CVE-2026-12773" ],
  "summary" : "LiteLLM: MCP Proxy Has Improper Authentication",
  "details" : "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "litellm"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.84.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-12773"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2c"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-12773"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2491112"
  }, {
    "type" : "WEB",
    "url" : "https://gist.github.com/YLChen-007/3cfaad10a69d7a15e4d4d458cb53309e"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/BerriAI/litellm"
  }, {
    "type" : "WEB",
    "url" : "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12773.json"
  }, {
    "type" : "WEB",
    "url" : "https://vuldb.com/cve/CVE-2026-12773"
  }, {
    "type" : "WEB",
    "url" : "https://vuldb.com/submit/811282"
  }, {
    "type" : "WEB",
    "url" : "https://vuldb.com/vuln/372515"
  }, {
    "type" : "WEB",
    "url" : "https://vuldb.com/vuln/372515/cti"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287", "CWE-303" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-10T22:32:02Z",
    "nvd_published_at" : "2026-06-21T04:16:28Z"
  }
}