CVE-2026-2652: MLflow Unauthenticated Access To Certain FastAPI Vulnerability

HIGH
Advisory Identifier: GHSA-75cm-x2w3-8mgf
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CVSS 8.6
CWE-305
Published
Advisory Summary

CVE-2026-2652 is a HIGH (CVSS 8.6) unauthenticated access to certain fastapi vulnerability (CWE-305: Authentication Bypass by Primary Weakness) affecting MLflow libraries in the PyPI ecosystem. The issue involves unauthenticated access to certain fastapi routes. Remediation is available by upgrading affected packages to version 3.11.0.

CVE-2026-2652 at a Glance

CVE Identifier CVE-2026-2652
GHSA Identifier GHSA-75cm-x2w3-8mgf
Severity HIGH
CVSS v3.1 Base Score 8.6
CWE Classification CWE-305: Authentication Bypass by Primary Weakness
Affected Product MLflow
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 8.6

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/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 High (I:H)
Availability Low (A:L)

How to Fix CVE-2026-2652

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: 3.11.0 
pip install mlflow>=3.11.0
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 mlflow

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-2652, 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 3.11.0), 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-305: Authentication Bypass by Primary Weakness, where the authentication algorithm is sound, but the implemented mechanism can be bypassed as the result of a separate weakness that is primary to the authentication error. 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

A vulnerability in mlflow/mlflow versions 3.9.0 and earlier allows unauthenticated access to certain FastAPI routes when the server is started with authentication enabled (`--app-name basic-auth`) and served via uvicorn (ASGI). The FastAPI permission middleware only enforces authentication on `/gateway/` routes, leaving other routes such as the Job API (`/ajax-api/3.0/jobs/*`) and the OpenTelemetry trace ingestion API (`/v1/traces`) unprotected. This allows unauthenticated remote attackers to submit jobs, read job results, cancel running jobs, and inject arbitrary trace data into experiments. The issue arises from an architectural mismatch between Flask and FastAPI authentication mechanisms, where the `_find_fastapi_validator()` function fails to handle non-`/gateway/` paths, resulting in a complete authentication bypass. This vulnerability is fixed in version 3.10.0.

CVE-2026-2652 Affected MLflow Versions

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

References

NVD — CVE-2026-2652 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-2652
Security Fix Commit FIX COMMIT
https://github.com/mlflow/mlflow/commit/bb62e773263c14e9ba4d1a82fe72d0de2442c6aa
MLflow Source Repository REPOSITORY
https://github.com/mlflow/mlflow
huntr.com/bounties/5aeff5f0-4... WEB
https://huntr.com/bounties/5aeff5f0-49c7-4180-b5cb-c9a046f16756

Frequently Asked Questions

What is CVE-2026-2652?
CVE-2026-2652 is a security vulnerability in MLflow involving unauthenticated access to certain FastAPI routes under CWE-305: Authentication Bypass by Primary Weakness.
Which MLflow versions are affected?
Affected versions include releases prior to 3.11.0 across affected packages: mlflow.
What version fixes CVE-2026-2652?
Upgrading to 3.11.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is mlflow affected?
Yes, mlflow is affected in releases prior to 3.11.0. Upgrade your dependency to 3.11.0 or later.
What is the CVSS score of CVE-2026-2652?
CVE-2026-2652 has a CVSS v3.1 base score of 8.6 (HIGH) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L.
What CWE is associated with CVE-2026-2652?
CVE-2026-2652 is classified under CWE-305: Authentication Bypass by Primary Weakness (The authentication algorithm is sound, but the implemented mechanism can be bypassed as the result of a separate weakness that is primary to the authentication error.).
How can I check PyPI dependencies for CVE-2026-2652?
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-75cm-x2w3-8mgf",
  "modified" : "2026-05-21T19:35:52Z",
  "published" : "2026-05-15T03:30:37Z",
  "aliases" : [ "CVE-2026-2652" ],
  "summary" : "MLflow: unauthenticated access to certain FastAPI routes",
  "details" : "A vulnerability in mlflow/mlflow versions 3.9.0 and earlier allows unauthenticated access to certain FastAPI routes when the server is started with authentication enabled (`--app-name basic-auth`) and served via uvicorn (ASGI). The FastAPI permission middleware only enforces authentication on `/gateway/` routes, leaving other routes such as the Job API (`/ajax-api/3.0/jobs/*`) and the OpenTelemetry trace ingestion API (`/v1/traces`) unprotected. This allows unauthenticated remote attackers to submit jobs, read job results, cancel running jobs, and inject arbitrary trace data into experiments. The issue arises from an architectural mismatch between Flask and FastAPI authentication mechanisms, where the `_find_fastapi_validator()` function fails to handle non-`/gateway/` paths, resulting in a complete authentication bypass. This vulnerability is fixed in version 3.10.0.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "mlflow"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
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      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-2652"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mlflow/mlflow/commit/bb62e773263c14e9ba4d1a82fe72d0de2442c6aa"
  }, {
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    "url" : "https://github.com/mlflow/mlflow"
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    "type" : "WEB",
    "url" : "https://huntr.com/bounties/5aeff5f0-49c7-4180-b5cb-c9a046f16756"
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  "database_specific" : {
    "cwe_ids" : [ "CWE-305" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-21T19:35:52Z",
    "nvd_published_at" : "2026-05-15T03:16:23Z"
  }
}