CVE-2012-2737 in AccountsService
Summary
by MITRE
The user_change_icon_file_authorized_cb function in /usr/libexec/accounts-daemon in AccountsService before 0.6.22 does not properly check the UID when copying an icon file to the system cache directory, which allows local users to read arbitrary files via a race condition.
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Analysis
by VulDB Data Team • 12/06/2021
The vulnerability identified as CVE-2012-2737 resides within the AccountsService component of Linux desktop environments, specifically affecting versions prior to 0.6.22. This issue manifests in the user_change_icon_file_authorized_cb function which handles icon file operations for user accounts. The flaw represents a classic privilege escalation vector that exploits improper access controls and race condition vulnerabilities within the system's account management daemon.
The technical implementation of this vulnerability stems from inadequate validation of user identifiers during icon file processing operations. When a user attempts to change their account icon, the function fails to properly verify the effective user ID before executing file copy operations to the system cache directory. This missing authorization check creates a window where local attackers can manipulate the file system operations through race condition exploitation. The vulnerability specifically targets the uid validation mechanism that should ensure only authorized users can perform icon modifications, but the implementation falls short of properly enforcing these security boundaries.
Operationally, this vulnerability allows local users to escalate privileges and access arbitrary files on the system through a carefully orchestrated race condition attack. The attacker can exploit the timing gap between when the system checks permissions and when the actual file copy operation occurs. This race condition enables the unauthorized reading of files that should normally be restricted to specific user groups or system administrators. The impact extends beyond simple information disclosure, as it provides a pathway for further system compromise through privilege escalation to higher-privileged accounts or system services.
The vulnerability aligns with CWE-284 Access Control Issues, specifically addressing improper access control mechanisms in the accounts daemon service. From an attack framework perspective, this weakness maps to ATT&CK technique T1068, which covers local privilege escalation through exploitation of system vulnerabilities. The race condition aspect of this flaw also connects to ATT&CK technique T1059, representing how attackers can leverage system services to execute malicious operations. The attack surface is particularly concerning in multi-user environments where local users might attempt to gain unauthorized access to sensitive system files or user data.
Mitigation strategies for this vulnerability require immediate patching of AccountsService to version 0.6.22 or later, which implements proper UID validation and race condition prevention mechanisms. System administrators should also implement monitoring for unauthorized icon file changes and consider restricting write permissions to the system cache directory where user icons are stored. Additional protective measures include implementing proper file system access controls, using mandatory access controls such as SELinux or AppArmor, and conducting regular security audits of system services that handle user account modifications. The fix should ensure that all file operations within the accounts daemon properly validate user credentials and eliminate race conditions through atomic operations or proper synchronization mechanisms.