CVE-2018-6513 in Puppet Enterprise
Summary
by MITRE
Puppet Enterprise 2016.4.x prior to 2016.4.12, Puppet Enterprise 2017.3.x prior to 2017.3.7, Puppet Enterprise 2018.1.x prior to 2018.1.1, Puppet Agent 1.10.x prior to 1.10.13, Puppet Agent 5.3.x prior to 5.3.7, and Puppet Agent 5.5.x prior to 5.5.2, were vulnerable to an attack where an unprivileged user on Windows agents could write custom facts that can escalate privileges on the next puppet run. This was possible through the loading of shared libraries from untrusted paths.
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Analysis
by VulDB Data Team • 02/18/2020
The vulnerability identified as CVE-2018-6513 represents a critical privilege escalation flaw affecting multiple versions of Puppet Enterprise and Puppet Agent software on Windows systems. This vulnerability stems from improper handling of shared library loading mechanisms within the puppet agent execution environment, creating a pathway for unprivileged users to execute malicious code with elevated privileges during subsequent puppet runs. The flaw specifically impacts Windows agents where the system loads shared libraries from paths that are not properly validated or secured against unauthorized modifications.
The technical root cause of this vulnerability lies in the insecure loading of dynamic link libraries from untrusted directories within the Windows agent environment. When puppet executes and processes custom facts, it loads shared libraries from locations that can be manipulated by unprivileged users. This behavior aligns with CWE-427 Uncontrolled Search Path Element, where the application searches for libraries in paths that can be influenced by attackers. The vulnerability creates a condition where an attacker can place malicious DLL files in directories that puppet will subsequently load, effectively allowing code execution with the privileges of the puppet agent process.
The operational impact of this vulnerability is significant as it enables a low-privilege attacker to escalate their privileges to the level of the puppet agent service account, which typically runs with elevated permissions. During the next puppet run, the malicious shared library gets loaded and executed, potentially allowing the attacker to gain persistent access to the system, execute arbitrary commands, or escalate privileges further. This represents a classic privilege escalation vector that can be exploited in environments where puppet agents are configured to run with administrative privileges. The vulnerability is particularly concerning in enterprise environments where puppet is used for system management and configuration, as it can be leveraged to compromise entire infrastructure domains.
The exploitation of this vulnerability requires an unprivileged user to have write access to specific directories on the Windows agent system, typically within the puppet agent installation paths or related shared library directories. The attack scenario involves placing a malicious DLL file in one of these locations, which is then loaded during the next puppet execution cycle. This follows the ATT&CK technique T1068 Exploitation for Privilege Escalation, where adversaries leverage software vulnerabilities to gain elevated privileges. The vulnerability is further exacerbated by the fact that puppet agent processes often run with high privileges to perform system configuration tasks, making the privilege escalation particularly impactful.
Organizations should implement immediate mitigations including applying the vendor-provided patches for all affected versions of Puppet Enterprise and Puppet Agent software. System administrators should also implement strict directory permissions on puppet agent installation directories, ensuring that only authorized users can write to these locations. The principle of least privilege should be enforced by configuring puppet agents to run with minimal required privileges rather than administrative rights. Additional security measures include monitoring for unauthorized file modifications in puppet agent directories and implementing file integrity monitoring solutions to detect malicious DLL placements. The vulnerability highlights the importance of secure library loading practices and proper input validation in system management tools, particularly those that execute with elevated privileges in enterprise environments.