CVE-2017-2295 in puppet
Summary
by MITRE
Versions of Puppet prior to 4.10.1 will deserialize data off the wire (from the agent to the server, in this case) with a attacker-specified format. This could be used to force YAML deserialization in an unsafe manner, which would lead to remote code execution. This change constrains the format of data on the wire to PSON or safely decoded YAML.
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Analysis
by VulDB Data Team • 10/22/2019
The vulnerability identified as CVE-2017-2295 represents a critical remote code execution flaw in Puppet configuration management software affecting versions prior to 4.10.1. This vulnerability stems from improper handling of data serialization formats during network communication between Puppet agents and servers, creating a pathway for attackers to manipulate deserialization processes and execute arbitrary code on affected systems. The flaw specifically manifests when the Puppet server deserializes data received from agents, allowing malicious actors to specify arbitrary deserialization formats that could be exploited for unauthorized system access.
The technical exploitation of this vulnerability occurs through unsafe YAML deserialization practices that were present in earlier Puppet versions. When an attacker can influence the data format being deserialized, they can craft malicious payloads that leverage the YAML deserialization mechanism to execute commands on the target system. This type of vulnerability falls under the CWE-502 category, which specifically addresses "Deserialization of Untrusted Data" as a critical security weakness. The vulnerability is particularly dangerous because it allows remote attackers to bypass authentication mechanisms and execute arbitrary code with the privileges of the Puppet server process, potentially leading to complete system compromise.
The operational impact of CVE-2017-2295 extends beyond simple remote code execution to encompass full system compromise and potential lateral movement within network environments. Organizations relying on Puppet for configuration management face significant risk as attackers could leverage this vulnerability to establish persistent access, exfiltrate sensitive configuration data, or use the compromised Puppet server as a launch point for attacks against other systems within the network infrastructure. The vulnerability affects the core communication protocols used by Puppet agents to report status and receive configuration updates, making it particularly dangerous for enterprise environments where Puppet is extensively deployed for system management and automation.
Security mitigations for this vulnerability primarily involve upgrading to Puppet version 4.10.1 or later, which implements proper constraints on data format handling and enforces the use of PSON (Perl Structured Data) or safely decoded YAML formats. Organizations should also implement network segmentation and monitoring to detect unusual communication patterns between Puppet agents and servers, as well as apply additional security controls such as firewall rules that restrict direct agent-to-server communication where possible. The remediation process should include thorough testing of the updated Puppet environment to ensure that existing configurations continue to function correctly while implementing the security hardening measures that prevent unsafe deserialization operations. This vulnerability demonstrates the critical importance of proper input validation and serialization handling in distributed systems, aligning with ATT&CK technique T1059.001 for command and scripting interpreter execution through remote access capabilities.