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CVE-2026-4035: Environment Variable Resolution Vulnerability in mlflow/mlflow

• Severity: high (CVSS 7.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-06-03 · updated 2026-08-14
• Weakness: CWE-201

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.

Affected products

• mlflow/mlflow: before 3.11.0 — fixed in 3.11.0

How to fix

Upgrade to a fixed version: mlflow/mlflow 3.11.0. Check the vendor advisory for mitigations.

References

• https://github.com/mlflow/mlflow/commit/4a3f2f720cb4f058c9e0c5b883e0acc9ab64a7f3
• https://huntr.com/bounties/f8e591a0-0f19-4910-b82e-16c9956f2233
• https://access.redhat.com/security/cve/CVE-2026-4035
• https://bugzilla.redhat.com/show_bug.cgi?id=2484318
• https://huntr.com/bounties/f8e591a0-0f19-4910-b82e-16c9956f2233
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4035.json

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