CVE-2011-5098 in Chef Infra
Summary
by MITRE
chef-server-api/app/controllers/clients.rb in Chef Server in Chef before 0.9.20, and 0.10.x before 0.10.6, does not require administrative privileges for creating admin clients, which allows remote authenticated users to bypass intended access restrictions by leveraging read permission for the validation key and executing a knife client create command with the --admin option.
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Analysis
by VulDB Data Team • 02/05/2025
The vulnerability described in CVE-2011-5098 represents a critical access control flaw within the Chef Server authentication system that undermines the security model designed to protect administrative resources. This issue affects Chef Server versions prior to 0.9.20 and 0.10.x versions prior to 0.10.6, where the system fails to properly enforce administrative privileges during client creation operations. The flaw specifically resides in the clients.rb controller file within the chef-server-api application, which governs how client entities are managed within the Chef infrastructure. The vulnerability stems from insufficient authorization checks that should normally prevent non-administrative users from creating administrative client accounts, thereby allowing privilege escalation through legitimate administrative commands.
The technical exploitation of this vulnerability occurs when authenticated users with read permissions for the validation key leverage the knife client create command with the --admin option to generate administrative client accounts. This represents a classic privilege escalation attack vector where legitimate administrative functionality is abused to bypass intended access controls. The validation key serves as a critical security mechanism in Chef Server that typically grants elevated privileges, and when combined with the lack of proper administrative privilege checks during client creation, it creates a pathway for unauthorized users to assume administrative roles within the Chef environment. This vulnerability directly maps to CWE-285, which addresses improper authorization in software systems, and demonstrates how weak access control enforcement can lead to privilege escalation attacks.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially compromise entire Chef-managed infrastructures. An attacker who gains read access to the validation key can effectively take control of the Chef Server's administrative functions, enabling them to modify node configurations, manage cookbook deployments, and potentially access sensitive configuration data across the entire infrastructure. This vulnerability particularly affects organizations that rely heavily on Chef for configuration management and automation, as it undermines the trust model that ensures only authorized administrators can make critical system changes. The attack requires only basic read permissions and knowledge of the knife client interface, making it accessible to attackers who may have gained limited access through other means.
Organizations should implement immediate mitigations including upgrading to Chef Server versions 0.9.20 or 0.10.6 and later, which contain the necessary access control fixes. The remediation process should also include reviewing and tightening access controls around the validation key, implementing proper role-based access controls, and monitoring for unauthorized client creation activities. Security teams should also consider implementing additional layers of authentication and authorization checks, particularly around administrative commands and resources. From an ATT&CK perspective, this vulnerability aligns with T1078 which covers valid accounts and privilege escalation techniques, and T1566 which covers credential access through various attack vectors. The vulnerability highlights the importance of principle of least privilege enforcement and demonstrates how even well-established configuration management tools can contain critical access control flaws that require careful monitoring and prompt remediation.