CVE-2011-3869 in Puppet
Summary
by MITRE
Puppet 2.7.x before 2.7.5, 2.6.x before 2.6.11, and 0.25.x allows local users to overwrite arbitrary files via a symlink attack on the .k5login file.
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Analysis
by VulDB Data Team • 11/24/2021
The vulnerability identified as CVE-2011-3869 represents a significant security flaw in the Puppet configuration management system affecting versions 2.7.x before 2.7.5, 2.6.x before 2.6.11, and 0.25.x. This issue stems from improper handling of symbolic links during the management of authentication files, specifically the .k5login file used for Kerberos authentication. The flaw enables local attackers to manipulate the file system by creating malicious symbolic links that can cause Puppet to overwrite arbitrary files with unintended content. This vulnerability directly relates to CWE-59, which describes improper handling of symbolic links, and falls under the broader category of path traversal and file manipulation attacks.
The technical implementation of this vulnerability occurs when Puppet processes the .k5login file during authentication setup. When Puppet encounters a .k5login file that is actually a symbolic link pointing to a target file outside the intended directory structure, the system fails to properly validate the link before performing file operations. This allows an attacker with local access to create a symbolic link with the name .k5login that points to a critical system file such as /etc/passwd or another sensitive location. When Puppet executes its file management routines, it follows the symbolic link and writes content to the target file instead of the intended location, effectively enabling arbitrary file overwrite capabilities.
The operational impact of this vulnerability extends beyond simple file overwrites, as it provides attackers with a mechanism to compromise system integrity and potentially escalate privileges. Local users can leverage this weakness to modify critical system files, inject malicious content, or disrupt normal system operations. The attack vector is particularly concerning because it requires only local system access, making it accessible to users who may not have elevated privileges but can still manipulate the file system. This vulnerability can be exploited to modify authentication files, configuration settings, or other sensitive system resources, potentially leading to persistent access or privilege escalation within the affected system.
Security practitioners should implement immediate mitigations including upgrading to Puppet versions 2.7.5, 2.6.11, or later 0.25.x releases where this vulnerability has been addressed. The fix involves implementing proper validation of symbolic links during file operations, ensuring that Puppet checks for and properly handles symbolic links before performing any write operations. Organizations should also conduct thorough security assessments of their Puppet configurations to identify any potential exploitation attempts and implement monitoring for suspicious file system activities. From an ATT&CK perspective, this vulnerability maps to technique T1059.001 (Command and Scripting Interpreter) and T1548.002 (Abuse Elevation Control Mechanism) as it can be used to establish persistent access through file manipulation. Additionally, implementing proper file system permissions and using tools like SELinux or AppArmor can provide additional defense-in-depth measures against such attacks.