CVE-2016-4755 in macOS
Summary
by MITRE
Terminal in Apple OS X before 10.12 uses weak permissions for the .bash_history and .bash_session files, which allows local users to obtain sensitive information via unspecified vectors.
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Analysis
by VulDB Data Team • 09/21/2022
The vulnerability identified as CVE-2016-4755 affects Apple macOS versions prior to 10.12, specifically targeting the terminal application's handling of shell history files. This security flaw stems from improper file permission settings that create exploitable conditions for local attackers to access sensitive information. The affected system components include the .bash_history and .bash_session files that are automatically created by the bash shell when users interact with the terminal application. These files contain command history and session information that may include sensitive data such as passwords, API keys, or other confidential information entered during terminal sessions. The weak permissions allow unauthorized local users to read these files directly, potentially exposing critical system information. This vulnerability represents a classic privilege escalation issue where local users can exploit insufficient access controls to gain unauthorized information disclosure. The flaw exists at the operating system level within the terminal application's file management processes, making it particularly concerning for environments where multiple users share the same system.
The technical implementation of this vulnerability involves the terminal application creating bash history files with overly permissive access controls. The .bash_history file typically stores command execution history while .bash_session maintains session-related information. When these files are created with world-readable permissions or without proper access control lists, any local user can access them through standard file system operations. This weakness allows for information disclosure attacks where attackers can extract previously executed commands, potentially including sensitive inputs such as passwords, database credentials, or other confidential data. The vulnerability operates through the standard file system access mechanisms rather than requiring complex exploitation techniques, making it particularly dangerous as it can be easily leveraged by any local user with basic system access. The underlying issue aligns with CWE-276, which addresses incorrect file permissions, and represents a failure in proper access control implementation within the operating system's terminal services.
The operational impact of CVE-2016-4755 extends beyond simple information disclosure, creating potential pathways for further attacks and system compromise. Local users who can access these history files may extract sensitive credentials or system information that can be used for privilege escalation, lateral movement, or additional attack vectors within the compromised system. The exposure of command history can reveal system administration activities, network configurations, or other sensitive operational data that could aid attackers in understanding system architecture and identifying potential targets. This vulnerability particularly affects multi-user systems where different users may have varying levels of clearance, as the weak permissions provide a consistent attack vector regardless of user privileges. The impact is significant in enterprise environments where security policies typically require strict access controls and information protection measures. Organizations using affected macOS versions may experience compliance violations and increased risk of data breaches due to the unauthorized access to potentially sensitive information stored in these history files.
Mitigation strategies for CVE-2016-4755 should prioritize immediate system updates to macOS 10.12 or later versions where Apple has addressed the permission handling issue. System administrators should conduct thorough audits of existing terminal history files to identify any potential exposure and implement proper file permission controls manually if immediate updates are not feasible. The recommended approach includes setting restrictive permissions on bash history files, typically using chmod 600 to ensure only the file owner can read and write these sensitive files. Additionally, organizations should implement monitoring solutions to detect unauthorized access attempts to these files and establish regular security assessments to identify similar permission-related vulnerabilities across the system infrastructure. The mitigation efforts should align with security frameworks such as the NIST Cybersecurity Framework and follow the principle of least privilege as outlined in the MITRE ATT&CK framework, specifically addressing the privilege escalation and credential access techniques that this vulnerability enables. Regular patch management processes should be enhanced to ensure timely deployment of security updates and prevent similar vulnerabilities from persisting in the system environment.