CVE-2016-5714 in Puppet Enterprise
Summary
by MITRE
Puppet Enterprise 2015.3.3 and 2016.x before 2016.4.0, and Puppet Agent 1.3.6 through 1.7.0 allow remote attackers to bypass a host whitelist protection mechanism and execute arbitrary code on Puppet nodes via vectors related to command validation, aka "Puppet Execution Protocol (PXP) Command Whitelist Validation Vulnerability."
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Analysis
by VulDB Data Team • 11/26/2019
The CVE-2016-5714 vulnerability represents a critical security flaw in Puppet Enterprise and Puppet Agent software versions that allows remote attackers to bypass host whitelist protections and execute arbitrary code on targeted nodes. This vulnerability specifically affects Puppet Enterprise 2015.3.3 and 2016.x versions before 2016.4.0, along with Puppet Agent versions 1.3.6 through 1.7.0. The flaw exists within the Puppet Execution Protocol (PXP) command validation mechanism, which is responsible for controlling which commands can be executed on managed nodes. The vulnerability stems from inadequate validation of command parameters that are passed through the PXP protocol, allowing attackers to craft malicious payloads that circumvent the intended host whitelist restrictions.
The technical implementation of this vulnerability exploits weaknesses in the command validation logic within Puppet's execution framework. Attackers can manipulate command parameters to include unauthorized commands that would normally be blocked by the whitelist protection mechanism. This occurs because the validation process fails to properly sanitize or verify the input parameters before executing commands on target nodes. The flaw essentially allows an attacker to inject arbitrary commands that bypass the normal security controls designed to restrict which hosts can execute which commands. The vulnerability operates at the protocol level, making it particularly dangerous as it can be exploited without requiring local access to the target systems. This weakness is classified under CWE-20, "Improper Input Validation," which is a fundamental security principle that requires proper sanitization and validation of all inputs to prevent malicious code execution.
From an operational impact perspective, this vulnerability creates a severe risk for organizations relying on Puppet for configuration management and automation. The ability to execute arbitrary code on Puppet nodes means that attackers can potentially gain full control over managed systems, escalate privileges, or establish persistent backdoors within the infrastructure. The vulnerability affects the core security model of Puppet deployments, where the whitelist protection is designed to prevent unauthorized execution of commands across distributed systems. Organizations using Puppet for managing large-scale deployments face significant risk, as a successful exploitation could allow attackers to compromise multiple nodes simultaneously, potentially leading to complete system compromise. The remote exploit capability means that attackers do not need physical access to the systems or network proximity, making the vulnerability particularly dangerous in environments with limited network segmentation.
Security mitigations for CVE-2016-5714 primarily focus on immediate software updates and configuration hardening measures. Organizations should immediately upgrade to Puppet Enterprise 2016.4.0 or later versions, and Puppet Agent 1.7.1 or later to address the vulnerability. Additionally, network segmentation and firewall rules should be implemented to restrict access to Puppet master servers and agent communication ports. The ATT&CK framework categorizes this vulnerability under T1059, "Command and Scripting Interpreter," as it enables adversaries to execute arbitrary commands on compromised systems. Organizations should also implement monitoring for unusual command execution patterns and establish robust audit trails for Puppet operations. The vulnerability highlights the importance of proper input validation and the principle of least privilege in security design, where systems should only execute commands that are explicitly authorized. Regular security assessments and penetration testing should be conducted to identify similar validation flaws in other configuration management tools and automation frameworks that may be in use within the organization's infrastructure.