CVE-2026-4035 Environment Variable Resolution Vulnerability in mlflow/mlflow
Attackers can exfiltrate server environment variables via AI Gateway secrets, potentially leading to credential leakage and downstream code execution.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-4035?
CVE-2026-4035 is a critical vulnerability in Lfprojects Mlflow, published on 3 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
A vulnerability in mlflow/mlflow versions prior to 3.11.0 allows for the resolution of environment variables in AI Gateway secrets, which can be exploited to exfiltrate sensitive server-side environment credentials to an attacker-controlled endpoint. This issue arises because the `api_key` field in gateway secrets can accept `$ENV_VAR` references, which are resolved against the MLflow server's environment during runtime. The resolved secrets are then sent in provider authentication headers to the configured upstream `api_base`. This vulnerability can be exploited by low-privileged authenticated users in basic-auth deployments or by unauthenticated users in default deployments without `basic-auth`. The impact includes potential leakage of sensitive credentials such as cloud artifact credentials (`AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY`), which could lead to artifact poisoning and cross-boundary code execution in downstream environments. The issue is fixed in version 3.11.0.
Weakness: CWE-201
Which versions are affected by CVE-2026-4035?
4 open source packages ship an affected version, including mlflow. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
mlflow Bitnami | All versions | 3.11.0 |
mlflow PyPI | All versions | 3.11.0 |
mlflow PyPI | All versions | 3.11.0 |
mlflow PyPI | All versions | 3.11.0 |
Products include Lfprojects Mlflow.
How do I fix CVE-2026-4035?
Upgrade mlflow to 3.11.0 or later.
Is CVE-2026-4035 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4035 exists.
Other vulnerabilities in Lfprojects Mlflow
- CVE-2026-64849 MLflow Server-Side Request Forgery
- CVE-2025-15379 Command Injection in mlflow/mlflow
- CVE-2024-0520 Remote Code Execution due to Full Controlled File Write in mlflow/mlflow
- CVE-2023-6977 Path Traversal: '\..\filename'
- CVE-2023-6709 Improper Neutralization of Special Elements Used in a Template Engine in mlflow/mlflow
Sources
Also known as BIT-mlflow-2026-4035, CLSA-2026-1783904618, CLSA-2026-1787296483, GHSA-g35p-px32-whv6, PYSEC-2026-2222.