CVE-2011-3872 in Puppet Enterprise Users
Summary
by MITRE
Puppet 2.6.x before 2.6.12 and 2.7.x before 2.7.6, and Puppet Enterprise (PE) Users 1.0, 1.1, and 1.2 before 1.2.4, when signing an agent certificate, adds the Puppet master s certdnsnames values to the X.509 Subject Alternative Name field of the certificate, which allows remote attackers to spoof a Puppet master via a man-in-the-middle (MITM) attack against an agent that uses an alternate DNS name for the master, aka "AltNames Vulnerability."
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Analysis
by VulDB Data Team • 01/05/2025
The CVE-2011-3872 vulnerability represents a critical certificate generation flaw in Puppet configuration management software that fundamentally undermines the security of certificate-based authentication. This vulnerability affects Puppet versions 2.6.x prior to 2.6.12 and 2.7.x prior to 2.7.6, as well as Puppet Enterprise Users versions 1.0, 1.1, and 1.2 prior to 1.2.4. The flaw occurs during the certificate signing process when the Puppet master server incorporates its own certdnsnames values into the X.509 Subject Alternative Name field of agent certificates. This technical implementation error creates a significant security gap that enables remote attackers to conduct man-in-the-middle attacks against Puppet agents.
The vulnerability stems from improper certificate generation practices where the Puppet master server automatically includes its own DNS names in the certificate Subject Alternative Name extension without proper validation or sanitization. When agents connect to a Puppet master using an alternate DNS name, the certificate validation process fails to properly verify that the certificate is intended for the specific host name being used for communication. This creates a scenario where an attacker can intercept communications between agents and masters by presenting a certificate that includes the legitimate master's DNS names in the Subject Alternative Name field, effectively allowing certificate spoofing attacks.
The operational impact of this vulnerability is severe as it completely undermines the trust model that Puppet relies upon for secure communication between agents and masters. Attackers can exploit this weakness to perform successful man-in-the-middle attacks against Puppet agents that use alternate DNS names for master connectivity, potentially allowing them to intercept and modify configuration data, execute arbitrary code on managed nodes, or gain unauthorized access to sensitive infrastructure information. The vulnerability affects the fundamental security assurances that certificate-based authentication provides, making it possible for attackers to establish trust relationships with Puppet agents without proper authentication.
This vulnerability aligns with CWE-310, which addresses cryptographic weaknesses, specifically focusing on improper certificate handling and validation. The flaw also maps to ATT&CK technique T1552.001, which covers "Unsecured Credentials," as it enables attackers to compromise the secure communication channels that Puppet uses to maintain configuration integrity. Organizations using Puppet in production environments face significant risk from this vulnerability, as it essentially removes the cryptographic protection that should prevent unauthorized parties from impersonating Puppet masters. The issue particularly affects environments where Puppet masters are accessed using DNS names different from those configured in the certdnsnames parameter, creating a direct attack vector for network-based adversaries.
Mitigation strategies for CVE-2011-3872 require immediate patching of affected Puppet versions to 2.6.12 or later, 2.7.6 or later, or Puppet Enterprise Users 1.2.4 or later. Organizations should also review their Puppet master configurations to ensure that certdnsnames values are properly validated and sanitized during certificate generation. Network administrators should implement additional monitoring to detect unusual certificate requests or certificate validation failures, while security teams should conduct comprehensive audits of all Puppet-managed infrastructure to identify potentially compromised agents. The vulnerability highlights the importance of proper certificate management practices and the need for thorough validation of certificate attributes before deployment in production environments.