CVE-2012-1989 in Puppet Enterprise Users
Summary
by MITRE
telnet.rb in Puppet 2.7.x before 2.7.13 and Puppet Enterprise (PE) 1.2.x, 2.0.x, and 2.5.x before 2.5.1 allows local users to overwrite arbitrary files via a symlink attack on the NET::Telnet connection log (/tmp/out.log).
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Analysis
by VulDB Data Team • 12/05/2021
The vulnerability identified as CVE-2012-1989 represents a critical file system security flaw in Puppet configuration management software that affects multiple versions of both the open source Puppet and its enterprise variant Puppet Enterprise. This vulnerability specifically targets the telnet.rb component within Puppet's ruby libraries, where improper handling of temporary files creates an exploitable race condition that enables local attackers to manipulate the system's file permissions and overwrite arbitrary files on the target system.
The technical implementation of this vulnerability stems from the insecure creation of temporary files within the /tmp directory, specifically the /tmp/out.log file used for logging NET::Telnet connection activities. When Puppet establishes telnet connections, it creates this temporary log file without proper security measures to prevent symbolic link attacks. The flaw occurs because the application creates the log file using a predictable path and does not validate whether the target path is a symbolic link or if it points to a location where an attacker can manipulate the file system. This creates a classic race condition scenario where an attacker can create a symbolic link with the same name as the target temporary file, causing the application to write data to an attacker-controlled location instead of the intended log file.
From an operational perspective, this vulnerability poses significant risks to systems running affected Puppet versions as it allows local users to potentially overwrite any file on the system with data from the telnet connection logs. The impact extends beyond simple file overwrites since attackers can leverage this to modify critical system files, configuration files, or even executable binaries, potentially leading to privilege escalation or complete system compromise. The vulnerability is particularly dangerous in environments where Puppet is used for system management, as the compromised system could be used to maintain persistent access or to escalate privileges within the managed infrastructure.
The attack vector for this vulnerability requires local system access, making it a local privilege escalation or lateral movement threat that can be particularly dangerous in multi-tenant environments or when Puppet is used with elevated privileges. Security researchers have categorized this vulnerability under CWE-367 which specifically addresses the Time-of-Check to Time-of-Use (TOCTOU) race condition, while threat actors could map this to ATT&CK technique T1059.007 for executing malicious code through command-line interfaces, or T1548.002 for privilege escalation via file permissions manipulation. Organizations running affected versions of Puppet should immediately apply the patches released in Puppet 2.7.13 and PE 2.5.1, which address the issue by implementing proper file validation and secure temporary file creation practices that prevent symbolic link attacks.
The remediation strategy involves updating to patched versions of Puppet software, but organizations should also implement additional security controls such as monitoring for unusual file system activities in the /tmp directory, implementing proper file system permissions, and ensuring that the Puppet service runs with minimal required privileges. System administrators should conduct thorough audits of their Puppet configurations to identify any custom modules that might be vulnerable to similar issues, and implement proper file system hardening measures to prevent attackers from creating symbolic links in temporary directories. This vulnerability demonstrates the importance of secure temporary file handling practices and highlights the need for thorough security testing of file system operations, particularly in privilege escalation scenarios where the security of temporary file creation can lead to complete system compromise.