CVE-2016-2786 in Puppet
Summary
by MITRE
The pxp-agent component in Puppet Enterprise 2015.3.x before 2015.3.3 and Puppet Agent 1.3.x before 1.3.6 does not properly validate server certificates, which might allow remote attackers to spoof brokers and execute arbitrary commands via a crafted certificate.
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Analysis
by VulDB Data Team • 01/15/2019
The pxp-agent component in Puppet Enterprise and Puppet Agent versions prior to specific patches exhibits a critical certificate validation vulnerability that fundamentally undermines the security of the automated infrastructure management system. This flaw exists within the secure communication framework that Puppet uses to establish trust between agents and servers, creating a pathway for malicious actors to bypass authentication mechanisms and gain unauthorized access to managed systems.
The technical implementation of this vulnerability stems from insufficient certificate validation logic within the pxp-agent module which is responsible for establishing secure communication channels between Puppet agents and the central Puppet master server. When the agent receives a server certificate during the communication handshake, it fails to properly verify the certificate's authenticity, validity, and trust chain. This weakness allows attackers to generate or obtain a malicious certificate that appears legitimate to the agent, thereby enabling man-in-the-middle attacks without proper authentication.
The operational impact of this vulnerability extends far beyond simple network interception, as it provides attackers with the capability to execute arbitrary commands on target systems. Once an attacker successfully spoofs a legitimate broker certificate, they can inject malicious code into the Puppet infrastructure, potentially compromising the entire managed environment. This vulnerability directly enables privilege escalation and persistent access, making it particularly dangerous in enterprise environments where Puppet is used to manage critical infrastructure components.
This vulnerability aligns with CWE-295, which addresses improper certificate validation, and maps to ATT&CK technique T1078.004 for valid accounts and T1566 for malicious file execution. The attack vector typically involves the attacker obtaining a certificate that appears to be from a legitimate Puppet server, then using this certificate to establish a trusted connection with the agent. This connection allows the attacker to execute Puppet manifests and commands with the privileges of the agent, effectively providing them with a foothold in the target environment.
Organizations should immediately implement mitigations including updating to patched versions of Puppet Enterprise 2015.3.3 or later and Puppet Agent 1.3.6 or later, which contain proper certificate validation mechanisms. Network segmentation and monitoring should be implemented to detect unusual certificate exchange patterns, while certificate pinning techniques can provide additional protection layers. Regular security audits of the Puppet infrastructure should verify that all certificates are properly validated and that no unauthorized certificates have been introduced into the system. The vulnerability represents a critical security gap that requires immediate remediation to prevent potential compromise of automated infrastructure management systems.