CVE-2015-4100 in Puppet Enterprise
Summary
by MITRE
Puppet Enterprise 3.7.x and 3.8.0 might allow remote authenticated users to manage certificates for arbitrary nodes by leveraging a client certificate trusted by the master, aka a "Certificate Authority Reverse Proxy Vulnerability."
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Analysis
by VulDB Data Team • 01/27/2021
The vulnerability identified as CVE-2015-4100 represents a critical security flaw in Puppet Enterprise versions 3.7.x and 3.8.0 that enables remote authenticated attackers to manipulate certificate management for arbitrary nodes within the system. This vulnerability operates through a sophisticated manipulation of the certificate authority infrastructure, specifically targeting the trust relationships between client certificates and the Puppet master server. The flaw stems from improper validation of certificate requests that allows malicious actors to exploit the certificate authority reverse proxy mechanism, effectively granting them unauthorized administrative capabilities over nodes they should not be able to control.
The technical implementation of this vulnerability involves the exploitation of trust relationships within the Puppet certificate management system. When a client certificate is presented to the Puppet master, the system should validate that the certificate belongs to the requesting node and that the node is authorized to perform the requested operations. However, in affected versions, the system fails to properly verify the certificate chain and trust relationships, allowing an attacker with valid credentials to submit certificate requests that appear to originate from other nodes within the infrastructure. This creates a reverse proxy scenario where the master inadvertently trusts certificates from unauthorized sources, effectively allowing attackers to assume the identity of other nodes and perform administrative operations on them.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it fundamentally compromises the integrity of the Puppet Enterprise certificate management system. Attackers can leverage this vulnerability to request certificates for nodes they do not own, potentially gaining access to sensitive configuration data, executing arbitrary code on target nodes, and performing unauthorized modifications to the infrastructure. The implications are particularly severe in environments where Puppet is used for critical infrastructure management, as this vulnerability could enable attackers to compromise entire node fleets by manipulating certificate trust relationships. The vulnerability also violates fundamental security principles of certificate-based authentication and undermines the trust model that Puppet Enterprise relies upon for secure node management.
This vulnerability aligns with CWE-295, which addresses "Improper Certificate Validation," and represents a specific instance of trust mismanagement in certificate-based systems. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and credential access, specifically targeting the credential management and defense evasion domains. The attack vector requires authentication, making it a post-authentication vulnerability that can be exploited by attackers who have already gained access to the Puppet Enterprise environment through other means. Organizations using Puppet Enterprise should consider this vulnerability as part of a broader attack surface assessment, particularly in environments where certificate management is critical for infrastructure security. The vulnerability's impact is amplified in multi-tenant environments where different teams or organizations share the same Puppet infrastructure, as attackers could potentially compromise nodes belonging to other users or departments.
Mitigation strategies for CVE-2015-4100 should include immediate patching of affected Puppet Enterprise versions to the latest releases that contain the necessary certificate validation fixes. Organizations should also implement additional monitoring of certificate requests and unusual certificate management activities within their Puppet infrastructure, as anomalous certificate issuance patterns could indicate exploitation attempts. Network segmentation and access controls should be reviewed to limit the scope of potential impact, while certificate lifecycle management processes should be strengthened to ensure proper validation of all certificate requests. Security teams should also consider implementing certificate transparency measures and regular audits of certificate trust relationships to detect and prevent similar vulnerabilities from being exploited in other parts of the infrastructure. The remediation process should include thorough testing of patched systems to ensure that legitimate certificate management operations continue to function properly while the vulnerability is addressed.