CVE-2009-3369 in BackupPC
Summary
by MITRE
CgiUserConfigEdit in BackupPC 3.1.0, when SSH keys and Rsync are in use in a multi-user environment, does not restrict users from the ClientNameAlias function, which allows remote authenticated users to read and write sensitive files by modifying ClientNameAlias to match another system, then initiating a backup or restore.
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Analysis
by VulDB Data Team • 09/08/2025
The vulnerability identified as CVE-2009-3369 affects BackupPC version 3.1.0 and represents a critical access control flaw that undermines the security of multi-user environments utilizing SSH keys and Rsync protocols. This issue stems from insufficient input validation and privilege separation within the CgiUserConfigEdit component, which serves as the web-based configuration interface for BackupPC administrators and users. The vulnerability specifically targets the ClientNameAlias function, which should normally be restricted to prevent unauthorized access to system resources and configuration data across different client environments.
The technical flaw manifests when authenticated users exploit the lack of proper authorization checks in the ClientNameAlias parameter handling. This function, designed to provide aliases for client names, becomes a vector for privilege escalation when improperly restricted. Attackers can manipulate the ClientNameAlias value to reference another system's client configuration, effectively bypassing normal access controls that should prevent users from accessing or modifying data belonging to different clients. This flaw operates under the broader category of insufficient authorization checks, which maps to CWE-285 and aligns with ATT&CK technique T1078 for valid accounts and privilege escalation.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables both read and write operations on sensitive system files across different client environments. An attacker with valid authentication credentials can leverage this flaw to perform unauthorized backups or restores, potentially leading to data corruption, information leakage, or complete system compromise. The vulnerability is particularly dangerous in multi-user environments where different users manage different client systems, as it allows lateral movement and privilege escalation without requiring additional authentication mechanisms or elevated privileges. This creates a scenario where a low-privilege user can effectively gain access to the configuration and data of other users' systems, undermining the fundamental security model of isolated client environments.
Mitigation strategies for CVE-2009-3369 should focus on implementing proper input validation and access control mechanisms within the BackupPC application. Organizations should immediately upgrade to patched versions of BackupPC that address this authorization flaw, as the vulnerability affects the core configuration management functionality. System administrators should also implement additional monitoring and logging of configuration changes, particularly those involving client name aliases, to detect unauthorized modifications. Network segmentation and principle of least privilege should be enforced to limit the scope of potential damage from compromised accounts. The vulnerability demonstrates the critical importance of proper access control implementation in web-based management interfaces, particularly when dealing with multi-user environments where different users require access to different system resources. Organizations should also consider implementing additional security controls such as mandatory access controls, regular security audits, and comprehensive user privilege management to prevent similar issues from occurring in other applications. This vulnerability serves as a reminder of the importance of proper authorization checking in all user-facing interfaces, especially those that handle system configuration and data management operations.