CVE-2016-2787 in Puppet Enterprise
Summary
by MITRE
The Puppet Communications Protocol in Puppet Enterprise 2015.3.x before 2015.3.3 does not properly validate certificates for the broker node, which allows remote non-whitelisted hosts to prevent runs from triggering via unspecified vectors.
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Analysis
by VulDB Data Team • 09/01/2020
The vulnerability described in CVE-2016-2787 represents a critical security flaw within the Puppet Communications Protocol of Puppet Enterprise 2015.3.x versions prior to 2015.3.3. This issue stems from inadequate certificate validation mechanisms that govern communications between nodes in the Puppet infrastructure, specifically affecting the broker node component that serves as a central communication hub for orchestration and configuration management tasks. The flaw creates a significant attack surface that undermines the integrity and availability of Puppet-managed environments through improper certificate validation processes.
The technical implementation of this vulnerability involves the failure to properly validate certificates presented by broker nodes during the communication handshake process. This certificate validation weakness allows malicious actors to exploit the system by presenting forged or unauthorized certificates that would otherwise be rejected by proper validation procedures. The vulnerability operates at the transport layer of the Puppet communications stack, where certificate authentication is supposed to establish trust relationships between nodes. Without proper validation, attackers can manipulate the certificate exchange process to inject unauthorized nodes or disrupt legitimate communication flows.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it fundamentally compromises the security model of Puppet Enterprise deployments. Remote attackers who can establish connections to the broker node can prevent legitimate configuration runs from executing, effectively disrupting the automation and management capabilities that organizations rely upon for maintaining consistent system states. This disruption can cascade through entire infrastructure environments, as Puppet is commonly used for managing large-scale deployments where configuration consistency and automated updates are critical for operational efficiency and security compliance.
This vulnerability aligns with CWE-295, which addresses "Improper Certificate Validation" in network communication protocols, and demonstrates how insufficient certificate validation can lead to serious security implications. The attack vector described in the CVE corresponds to ATT&CK technique T1070.004, which involves "File and Directory Permissions Modification" through manipulation of communication protocols. Organizations using affected Puppet Enterprise versions face the risk of unauthorized access to their configuration management infrastructure, potentially leading to complete compromise of their automated deployment systems and associated security policies.
The recommended mitigation strategy involves upgrading to Puppet Enterprise 2015.3.3 or later versions where the certificate validation mechanisms have been properly implemented and tested. System administrators should also implement additional network-level controls such as firewall rules that restrict access to broker node communication ports, and consider implementing network segmentation to limit exposure of critical Puppet infrastructure components. Regular certificate audits and monitoring of communication patterns should be established to detect potential exploitation attempts, while organizations should review their existing certificate management practices to ensure that proper validation procedures are in place for all components within their Puppet deployment environments.