CVE-2026-2635

MLflow Use of Default Password Authentication Bypass Vulnerability. This vulnerability allows remote attackers to bypass authentication on affected installations of MLflow. Authentication is not required to exploit this vulnerability. The specific flaw exists within the basic_auth.ini file. The file contains hard-coded default credentials. An attacker can leverage this vulnerability to bypass authentication and execute arbitrary code in the context of the administrator. Was ZDI-CAN-28256.

An attacker performs passive reconnaissance (Shodan, Censys) to identify internet-exposed MLflow instances. Using the publicly documented default credentials from basic_auth.ini — trivially extractable from the MLflow open-source repo — they authenticate as administrator with no exploitation tooling required. From there, they enumerate all registered models and experiments, exfiltrate proprietary models and training data, and inject a poisoned model version into the registry pointing to a backdoored artifact. The production serving infrastructure, configured to pull the 'latest' version from the registry, automatically deploys the malicious model. The attacker maintains persistence through the MLflow admin account while the poisoned model silently operates in production — potentially for weeks before detection.