CVE-2018-11751 in Puppet Agent
Summary
by MITRE
Previous versions of Puppet Agent didn't verify the peer in the SSL connection prior to downloading the CRL. This issue is resolved in Puppet Agent 6.4.0.
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Analysis
by VulDB Data Team • 03/12/2024
The vulnerability identified as CVE-2018-11751 represents a critical security flaw in Puppet Agent versions prior to 6.4.0 where the software failed to properly verify the peer identity during SSL connections used for downloading Certificate Revocation Lists. This weakness stems from insufficient certificate validation mechanisms that allowed for potential man-in-the-middle attacks during the CRL retrieval process. The issue specifically affects the SSL/TLS handshake implementation within Puppet's certificate management infrastructure, creating a window of opportunity for attackers to intercept and manipulate certificate revocation data.
The technical root cause of this vulnerability lies in the absence of proper peer verification during SSL connections, which is a fundamental security control that should ensure the authenticity of the communicating party. This flaw directly relates to CWE-295, which addresses improper certificate validation, and specifically targets the lack of hostname verification in SSL/TLS connections. The vulnerability allows an attacker positioned between the Puppet agent and the certificate authority to present a fake certificate during the CRL download process, potentially enabling them to bypass certificate revocation checks and maintain access to systems using compromised certificates.
The operational impact of this vulnerability is significant as it undermines the entire certificate trust model that Puppet relies upon for secure configuration management. When Puppet agents fail to verify peer identities during CRL downloads, they cannot reliably determine whether the certificate revocation information comes from a legitimate source or has been tampered with by an attacker. This creates a scenario where compromised certificates might not be properly detected and revoked, allowing malicious actors to continue operating within the network using stolen or compromised credentials. The vulnerability affects Puppet's ability to maintain secure communication channels and enforce certificate-based authentication policies.
Organizations using affected Puppet Agent versions face substantial risk of credential compromise and unauthorized access to their infrastructure. The vulnerability enables attackers to potentially inject false CRL information that could cause legitimate certificates to be incorrectly accepted, or conversely, valid certificates to be incorrectly rejected. This disruption of certificate validation processes can lead to service outages or security breaches that compromise the integrity of the entire Puppet-managed environment. The issue is particularly concerning in enterprise environments where Puppet is used extensively for configuration management and automated deployment processes.
The remediation for CVE-2018-11751 requires upgrading Puppet Agent to version 6.4.0 or later, which implements proper peer verification during SSL connections for CRL downloads. This upgrade ensures that the SSL/TLS handshake process includes hostname verification and certificate validation checks that prevent man-in-the-middle attacks. Organizations should also review their certificate management policies and ensure that all Puppet agents are properly configured to enforce strict certificate validation. Security teams should conduct thorough testing of the upgraded environment to verify that certificate revocation checking functions properly and that no regressions have occurred in the certificate management workflow. Additionally, organizations should implement monitoring for any suspicious certificate validation events that might indicate attempted exploitation of similar vulnerabilities. The fix addresses the underlying ATT&CK technique T1552.001, which involves credential access through the use of valid credentials, by restoring proper certificate validation controls that prevent unauthorized certificate trust manipulation.