# CVE-2026-33866: Authorization Bypass in MLflow AJAX Endpoint

> Attackers can bypass authorization checks to download unauthorized model artifacts from MLflow experiments via a vulnerable AJAX endpoint.

- **Severity:** Medium 5.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Apr 2026
- **Updated:** 14 Apr 2026
- **Also known as:** BIT-mlflow-2026-33866, GHSA-46r5-x6jq-v8g6, PYSEC-2026-94

## What is CVE-2026-33866?

CVE-2026-33866 is a medium-severity missing authorization vulnerability in Lfprojects Mlflow, published on 7 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-33866?

4 open source packages ship an affected version, including mlflow. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mlflow` | Bitnami | All versions | 3.11.1 |
| `mlflow` | PyPI | All versions | 3.11.0rc0 |
| `mlflow` | PyPI | All versions | 3.11.0rc0 |
| `mlflow` | PyPI | All versions | 3.11.0rc0 |

Products: Lfprojects Mlflow.

## How do I fix CVE-2026-33866?

Upgrade mlflow to a fixed version for your release line: 3.11.1 or 3.11.0rc0.

## Is CVE-2026-33866 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33866 exists.

## Other vulnerabilities in Lfprojects Mlflow

- [CVE-2026-64849](https://insights.sbomify.com/CVE-2026-64849/): MLflow Server-Side Request Forgery (critical 9.3, exploited in the wild)
- [CVE-2025-15379](https://insights.sbomify.com/CVE-2025-15379/): Command Injection in mlflow/mlflow (critical 10.0)
- [CVE-2024-0520](https://insights.sbomify.com/CVE-2024-0520/): Remote Code Execution due to Full Controlled File Write in mlflow/mlflow (critical 10.0)
- [CVE-2023-6977](https://insights.sbomify.com/CVE-2023-6977/): Path Traversal: '\..\filename' (critical 10.0)
- [CVE-2023-6709](https://insights.sbomify.com/CVE-2023-6709/): Improper Neutralization of Special Elements Used in a Template Engine in mlflow/mlflow (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33866 and fix it if it is affected.

What it is: CVE-2026-33866 is a medium-severity missing authorization vulnerability in Lfprojects Mlflow, published on 7 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33866 exists.

Affected packages and fixed versions:
- mlflow (Bitnami): affected all versions; fixed in 3.11.1
- mlflow (PyPI): affected all versions; fixed in 3.11.0rc0
- mlflow (PyPI): affected all versions; fixed in 3.11.0rc0
- mlflow (PyPI): affected all versions; fixed in 3.11.0rc0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-33866/ (Markdown: https://insights.sbomify.com/CVE-2026-33866/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33866
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33866
- OSV: https://osv.dev/vulnerability/CVE-2026-33866

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33866/
Summaries are generated and may contain mistakes; the official description above is the record.