CVE-2016-2785 in Puppet
Summary
by MITRE
Puppet Server before 2.3.2 and Ruby puppetmaster in Puppet 4.x before 4.4.2 and in Puppet Agent before 1.4.2 might allow remote attackers to bypass intended auth.conf access restrictions by leveraging incorrect URL decoding.
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Analysis
by VulDB Data Team • 08/23/2022
The vulnerability identified as CVE-2016-2785 affects Puppet Server versions prior to 2.3.2 and Ruby puppetmaster in Puppet 4.x versions before 4.4.2, as well as Puppet Agent versions before 1.4.2. This security flaw resides in the authentication and access control mechanisms of the Puppet configuration management system, which is widely deployed across enterprise environments for automating infrastructure management and configuration deployment. The vulnerability specifically targets the auth.conf file that defines access restrictions for various Puppet server endpoints and resources, making it a critical concern for organizations relying on Puppet for their infrastructure automation.
The technical flaw stems from incorrect URL decoding implementation within the Puppet server's authentication handling process. When processing incoming requests, the system fails to properly decode URL-encoded characters in resource paths, allowing malicious actors to craft specially formatted URLs that bypass intended access controls. This improper URL decoding creates a path traversal-like condition where attackers can manipulate the URL structure to access restricted resources that should only be available to authorized users or specific Puppet components. The vulnerability essentially allows an attacker to exploit the authentication system by crafting requests that appear to target legitimate resources but actually traverse to restricted areas due to the flawed decoding process.
The operational impact of this vulnerability is significant as it enables remote attackers to bypass authentication mechanisms that are fundamental to Puppet's security model. An attacker who can successfully exploit this vulnerability gains unauthorized access to restricted Puppet server resources, potentially allowing them to view sensitive configuration data, modify server settings, or access privileged endpoints that should be protected. This could lead to complete compromise of the Puppet infrastructure, enabling attackers to manipulate configuration management policies and potentially gain access to broader network resources that depend on Puppet for configuration control. The vulnerability is particularly dangerous because it can be exploited remotely without requiring prior authentication, making it an attractive target for attackers seeking to escalate privileges within Puppet-managed environments.
Organizations should immediately update their Puppet Server, puppetmaster, and Puppet Agent installations to versions that address this vulnerability. The affected versions include Puppet Server 2.3.2 and later, Puppet 4.x 4.4.2 and later, and Puppet Agent 1.4.2 and later. Security teams should also review their existing auth.conf files to ensure that access restrictions are properly configured and monitor for any suspicious authentication attempts that might indicate exploitation attempts. The vulnerability aligns with CWE-20 Improper Input Validation, specifically in how the system handles URL decoding and input validation for authentication requests. From an ATT&CK perspective, this vulnerability maps to T1078 Valid Accounts and T1566 Phishing, as it allows for privilege escalation through authentication bypass and could be exploited as part of a broader attack chain targeting infrastructure automation systems. Organizations should also implement network segmentation and monitoring to detect anomalous access patterns that might indicate exploitation attempts, particularly around Puppet server endpoints and configuration access requests.