CVE-2016-3096 in Ansible
Summary
by MITRE
The create_script function in the lxc_container module in Ansible before 1.9.6-1 and 2.x before 2.0.2.0 allows local users to write to arbitrary files or gain privileges via a symlink attack on (1) /opt/.lxc-attach-script, (2) the archived container in the archive_path directory, or the (3) lxc-attach-script.log or (4) lxc-attach-script.err files in the temporary directory.
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Analysis
by VulDB Data Team • 10/09/2024
The CVE-2016-3096 vulnerability represents a critical privilege escalation and arbitrary file write flaw within Ansible's lxc_container module, affecting versions prior to 1.9.6-1 and 2.x versions before 2.0.2.0. This vulnerability stems from insecure temporary file handling practices that create opportunities for local attackers to manipulate system files through symbolic link attacks. The flaw specifically targets four distinct file paths that are utilized during container operations, making it particularly dangerous as it can be exploited to gain elevated privileges or corrupt system files. The vulnerability operates at the intersection of privilege escalation and file system manipulation, creating a vector for attackers to compromise the integrity of containerized environments.
The technical implementation of this vulnerability exploits weak permissions and predictable file paths within the lxc_container module's create_script function. When Ansible processes container operations, it creates temporary files with predictable names in well-known locations such as /opt/.lxc-attach-script and temporary directories containing lxc-attach-script.log and lxc-attach-script.err files. Attackers can leverage symlink attacks to redirect these temporary file operations to arbitrary locations, effectively allowing them to write malicious content to files they would normally not have access to. This represents a classic insecure temporary file handling pattern that aligns with CWE-377 and CWE-378, which specifically address unsafe temporary file creation and weak file permissions. The vulnerability is particularly concerning because it can be exploited by unprivileged users to gain root privileges or modify critical system files.
The operational impact of CVE-2016-3096 extends beyond simple privilege escalation to encompass potential system compromise and data integrity violations. When exploited successfully, attackers can manipulate container environments to execute arbitrary code with elevated privileges, potentially leading to full system compromise. The vulnerability affects environments where Ansible is used for container management, particularly in automated deployment scenarios where privileged operations are performed. The attack vector is particularly insidious because it requires minimal privileges and can be executed through standard Ansible workflows, making it difficult to detect and prevent. This vulnerability is categorized under the MITRE ATT&CK framework as a privilege escalation technique, specifically targeting the 'Exploitation for Privilege Escalation' tactic and 'Local Port' or 'File and Directory Permissions Weakness' techniques.
Mitigation strategies for CVE-2016-3096 primarily focus on upgrading to patched versions of Ansible where the lxc_container module properly handles temporary files with secure permissions and predictable naming. Organizations should immediately update their Ansible installations to versions 1.9.6-1 or 2.0.2.0 and later, which address the insecure temporary file handling. Additionally, system administrators should implement proper file permission controls on the affected directories and ensure that temporary file creation uses secure methods such as creating files with restrictive permissions and using secure temporary directory locations. The vulnerability also highlights the importance of proper input validation and secure coding practices, particularly in modules that handle container operations. Security monitoring should include detection of symlink attacks and unusual file access patterns in the affected temporary directories. Organizations should also consider implementing principle of least privilege for Ansible execution environments and regularly audit system permissions to prevent exploitation of similar vulnerabilities in other modules.