CVE-2013-6412 in Augeas
Summary
by MITRE
The transform_save function in transform.c in Augeas 1.0.0 through 1.1.0 does not properly calculate the permission values when the umask contains a "7," which causes world-writable permissions to be used for new files and allows local users to modify the files via unspecified vectors.
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Analysis
by VulDB Data Team • 01/31/2022
The vulnerability identified as CVE-2013-6412 resides within the Augeas configuration management tool version 1.0.0 through 1.1.0, specifically within the transform_save function located in the transform.c source file. This flaw represents a critical security issue that stems from improper handling of file permission calculations during the file creation process. Augeas is widely used for parsing and modifying configuration files across various Unix-like systems, making this vulnerability particularly concerning for system administrators who rely on its functionality for maintaining system integrity.
The technical root cause of this vulnerability lies in how the transform_save function processes umask values when they contain the digit "7." Normally, umask values function as a bitmask that determines default file permissions by masking out specific permission bits from the default file creation mode. When a umask contains a "7," the calculation logic fails to properly interpret the permission values, resulting in the creation of files with world-writable permissions. This occurs because the bitwise operations used to determine final file permissions become malformed, causing the system to grant overly permissive access levels to newly created files.
The operational impact of this vulnerability is substantial as it creates a persistent security risk that can be exploited by local users through unspecified vectors. Since the vulnerability allows for world-writable permissions to be applied to new files, any user with access to the system can potentially modify these files and thereby compromise system security. This issue can lead to privilege escalation scenarios, configuration tampering, and potential data integrity violations. The unspecified vectors mentioned in the description suggest that multiple attack paths may exist, making the vulnerability particularly dangerous as attackers can leverage various methods to exploit the flawed permission calculation.
This vulnerability aligns with CWE-276, which addresses improper file permissions, and represents a classic case of inadequate input validation and permission handling in system-level software. From an ATT&CK framework perspective, this issue maps to T1068, which covers 'Exploitation for Privilege Escalation,' and potentially T1059, 'Command and Scripting Interpreter,' as attackers may use the compromised files to execute malicious code. The vulnerability also connects to T1546, 'Privilege Escalation,' since the ability to modify world-writable files can lead to broader system compromise. The flaw demonstrates poor security hygiene in the implementation of file creation and permission management functions, which is particularly concerning given Augeas's role in system configuration management where such tools are expected to maintain strict security controls.
Mitigation strategies should include immediate patching of affected Augeas versions to the latest stable releases that contain the fixed permission calculation logic. System administrators should also implement monitoring for unexpected file permission changes and conduct regular security audits of configuration file permissions. Additionally, organizations should consider implementing mandatory access controls and file integrity monitoring solutions to detect and prevent unauthorized modifications to critical system files. The fix typically involves correcting the bitwise operations in the transform_save function to properly handle all possible umask values, including those containing the digit "7," ensuring that file permissions are calculated correctly according to standard Unix permission models.