CVE-2026-33866: Mlflow MLflow Is Vulnerable To An Vulnerability

MODERATE
Advisory Identifier: GHSA-46r5-x6jq-v8g6
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CVSS 4.3
CWE-862
Published
Advisory Summary

CVE-2026-33866 is a MODERATE (CVSS 4.3) mlflow is vulnerable to an vulnerability (CWE-862: Missing Authorization) affecting Mlflow libraries in the PyPI ecosystem. The issue involves mlflow is vulnerable to an authorization bypass affecting the ajax endpoint. Remediation is available by upgrading affected packages to version 3.11.0rc0.

CVE-2026-33866 at a Glance

CVE Identifier CVE-2026-33866
GHSA Identifier GHSA-46r5-x6jq-v8g6
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-862: Missing Authorization
Affected Product Mlflow
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 4.3

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

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

How to Fix CVE-2026-33866

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

mlflow fixed: 3.11.0rc0 
pip install mlflow>=3.11.0rc0
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 mlflow

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-33866, inspect your installed packages using pip:

pip show mlflow

Analyze the terminal output to locate any version of Mlflow in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.11.0rc0), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-862: Missing Authorization, where the product does not perform an authorization check when an actor attempts to access a resource or perform an action. In Mlflow, 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

MLflow is vulnerable to an authorization bypass affecting the AJAX endpoint used to download saved model artifacts. Due to missing access‑control validation, a user without permissions to a given experiment can directly query this endpoint and retrieve model artifacts they are not authorized to access. This issue affects MLflow version through 3.10.1

CVE-2026-33866 Affected Mlflow Versions

1 component(s)
Fixed Versions:
3.11.0rc0
Product / Package Ecosystem Affected Versions Fixed Version
mlflow
pypi/mlflow
PyPI
< 3.11.0rc0
3.11.0rc0

References

NVD — CVE-2026-33866 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33866
Mlflow Source Repository REPOSITORY
https://github.com/mlflow/mlflow/pull/21708
Security Fix Commit FIX COMMIT
https://github.com/mlflow/mlflow/commit/005b959cacda05d1423356cfcbd9ebeda8ff96a7
afine.com/blogs/attacking-mlf... WEB
https://afine.com/blogs/attacking-mlflow-how-ml-artifacts-become-attack-vectors
cert.pl/en/posts/2026/04/cv... WEB
https://cert.pl/en/posts/2026/04/CVE-2026-33865
Mlflow Source Repository REPOSITORY
https://github.com/mlflow/mlflow
Mlflow Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/mlflow/PYSEC-2026-94.yaml

Frequently Asked Questions

What is CVE-2026-33866?
CVE-2026-33866 is a security vulnerability in Mlflow involving MLflow is vulnerable to an authorization bypass affecting the AJAX endpoint under CWE-862: Missing Authorization.
Which Mlflow versions are affected?
Affected versions include releases prior to 3.11.0rc0 across affected packages: mlflow.
What version fixes CVE-2026-33866?
Upgrading to 3.11.0rc0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is mlflow affected?
Yes, mlflow is affected in releases prior to 3.11.0rc0. Upgrade your dependency to 3.11.0rc0 or later.
What is the CVSS score of CVE-2026-33866?
CVE-2026-33866 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.
What CWE is associated with CVE-2026-33866?
CVE-2026-33866 is classified under CWE-862: Missing Authorization (The product does not perform an authorization check when an actor attempts to access a resource or perform an action.).
How can I check PyPI dependencies for CVE-2026-33866?
Run the dependency tree command: 'pip show mlflow'. 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-46r5-x6jq-v8g6",
  "modified" : "2026-06-06T00:57:58Z",
  "published" : "2026-04-07T15:30:50Z",
  "aliases" : [ "CVE-2026-33866" ],
  "summary" : "MLflow is vulnerable to an authorization bypass affecting the AJAX endpoint",
  "details" : "MLflow is vulnerable to an authorization bypass affecting the AJAX endpoint used to download saved model artifacts. Due to missing access‑control validation, a user without permissions to a given experiment can directly query this endpoint and retrieve model artifacts they are not authorized to access.\n\n \nThis issue affects MLflow version through 3.10.1",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "mlflow"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.11.0rc0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.10.1"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33866"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mlflow/mlflow/pull/21708"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mlflow/mlflow/commit/005b959cacda05d1423356cfcbd9ebeda8ff96a7"
  }, {
    "type" : "WEB",
    "url" : "https://afine.com/blogs/attacking-mlflow-how-ml-artifacts-become-attack-vectors"
  }, {
    "type" : "WEB",
    "url" : "https://cert.pl/en/posts/2026/04/CVE-2026-33865"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mlflow/mlflow"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/mlflow/PYSEC-2026-94.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-862" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-08T00:18:40Z",
    "nvd_published_at" : "2026-04-07T13:16:47Z"
  }
}