CVE-2018-16837 in Ansible
Summary
by MITRE
Ansible "User" module leaks any data which is passed on as a parameter to ssh-keygen. This could lean in undesirable situations such as passphrases credentials passed as a parameter for the ssh-keygen executable. Showing those credentials in clear text form for every user which have access just to the process list.
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Analysis
by VulDB Data Team • 05/30/2023
The vulnerability identified as CVE-2018-16837 resides within the Ansible user module implementation and represents a critical security flaw that exposes sensitive information through process visibility mechanisms. This issue specifically affects the handling of SSH key generation operations where the user module directly passes parameters to the ssh-keygen executable without proper sanitization or obfuscation. The flaw occurs when Ansible processes user account creation or modification tasks that involve SSH key management, creating a scenario where command-line arguments containing sensitive data become visible to any user with process listing privileges on the system.
The technical mechanism behind this vulnerability involves the direct invocation of external system commands through Ansible's user module functionality. When Ansible executes ssh-keygen with parameters that include passphrases, private keys, or other credential data, these values appear in the process table as command-line arguments. This behavior violates fundamental security principles regarding the handling of sensitive information and creates an attack surface where malicious actors with basic system access can extract credentials through simple process enumeration techniques. The vulnerability is particularly dangerous because it operates at the system level where process information is accessible to users with minimal privileges, making it exploitable in multi-tenant environments or shared system configurations.
The operational impact of CVE-2018-16837 extends beyond immediate credential exposure to encompass broader security implications for automated infrastructure management systems. Organizations relying on Ansible for user provisioning and key management face significant risks when sensitive data such as SSH passphrases, private key material, or other authentication tokens become visible through process monitoring. This exposure creates opportunities for privilege escalation attacks, lateral movement within networks, and unauthorized access to systems where Ansible is deployed. The vulnerability directly relates to CWE-200, which addresses the improper exposure of sensitive information, and aligns with ATT&CK technique T1059.003 for command and scripting interpreter, specifically targeting the execution of system commands with sensitive parameters. The risk is amplified in environments where multiple users share the same system or where monitoring tools automatically capture process information for troubleshooting purposes.
Mitigation strategies for this vulnerability require immediate attention through software updates and operational procedure adjustments. The primary remediation involves upgrading to Ansible versions that address this specific flaw through proper parameter sanitization and secure command execution practices. Organizations should implement additional controls such as restricting process visibility to authorized personnel only, implementing monitoring for suspicious process execution patterns, and establishing strict access controls around systems where Ansible is deployed. Security teams should also consider implementing runtime protections that prevent sensitive data from appearing in command-line arguments, such as using environment variables or temporary files for credential storage instead of command-line parameters. The vulnerability demonstrates the importance of secure coding practices in automation tools and highlights the need for comprehensive security testing of system management frameworks that interact with external executables containing sensitive data.