CVE-2012-0787 in Augeas
Summary
by MITRE
The clone_file function in transfer.c in Augeas before 1.0.0, when copy_if_rename_fails is set and EXDEV or EBUSY is returned by the rename function, allows local users to overwrite arbitrary files and obtain sensitive information via a bind mount on the (1) .augsave or (2) destination file when using the backup save option, or (3) .augnew file when using the newfile save option.
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Analysis
by VulDB Data Team • 01/10/2022
The CVE-2012-0787 vulnerability resides within the Augeas configuration management tool, specifically in the transfer.c file's clone_file function. This flaw manifests when the copy_if_rename_fails parameter is enabled, creating a dangerous condition where local attackers can exploit file system operations to overwrite arbitrary files and potentially access sensitive information. The vulnerability operates through a sophisticated attack vector that leverages the rename system call's error handling mechanisms to manipulate file system states. The issue affects Augeas versions prior to 1.0.0, making it a significant concern for systems relying on this configuration management tool for critical infrastructure management.
The technical exploitation occurs when the rename function returns either EXDEV (cross-device link) or EBUSY (device or resource busy) error codes, which are typically handled by attempting to copy files instead of renaming them. However, the implementation contains a race condition or improper handling of these specific error codes that allows attackers to manipulate the file system state through bind mounts. When Augeas attempts to save configuration changes using backup or newfile save options, the vulnerability becomes exploitable. The .augsave files are used during backup operations, while .augnew files are utilized in newfile save scenarios, creating multiple attack surfaces for potential exploitation.
The operational impact of this vulnerability extends beyond simple file overwrites, as it can lead to privilege escalation and information disclosure when attackers can manipulate files that contain sensitive configuration data or system credentials. The vulnerability represents a classic case of insecure file handling in a system management tool, where the backup and restore mechanisms become attack vectors. Attackers can leverage this flaw to overwrite critical system files, configuration files, or even files containing authentication tokens, potentially compromising entire system configurations. The local nature of the attack means that an attacker must already have access to the system, but the privilege escalation potential makes this particularly dangerous in multi-user environments where attackers might gain access through other means.
This vulnerability aligns with CWE-362, which describes "Concurrent Execution using Shared Resource with Improper Synchronization," and CWE-22, "Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')." The attack pattern follows ATT&CK technique T1059.007 for execution through shell commands, and T1070.004 for file and directory permissions modification. The flaw demonstrates poor error handling and insufficient validation of file system operations within the context of backup and restore functionality. Organizations should immediately update to Augeas version 1.0.0 or later to address this vulnerability, as the patch resolves the improper handling of rename error codes and implements proper file system state validation. System administrators should also review file permissions and access controls for Augeas-related directories to minimize potential impact if exploitation occurs, particularly focusing on the .augsave and .augnew file locations that are directly targeted by this vulnerability.