An authenticated command injection flaw in the btrbk backup tool permits unauthorized command execution, posing a high risk of system compromise.

The vulnerability exists in the ssh_filter_btrbk.sh script, which fails to use end-of-string anchors when validating commands. An authenticated user with restricted SSH access can append malicious commands to a valid btrbk prefix, leading to OS command injection with the privileges of the backup-target account.

The ability to execute arbitrary commands on a backup server represents a critical failure in security boundaries. Successful exploitation could lead to full unauthorized access to the backup target, potential data theft, or the compromise of secondary systems connected to the backup infrastructure. With a CVSS score of 8.7, this flaw is categorized as high severity due to the high impact on confidentiality, integrity, and availability.

Immediate Action: Upgrade to btrbk version 0.32.7 or later to implement the corrected command validation logic.

Proactive Monitoring: Review SSH authorized_keys files for anomalous forced commands and monitor system logs for unexpected shell activity or pipe-based command sequences.

Compensating Controls: If immediate patching is not possible, ensure that the SSH backup account is further restricted using minimal shell environments or by disabling shell access entirely if the deployment allows.

Public Exploit Available: No (exploit_available: false)

This vulnerability presents a significant risk to organizations relying on btrbk for automated backups. Given the potential for full command execution, administrators should prioritize the update to version 0.32.7 across all affected environments. Ensuring that SSH forced commands are strictly validated is essential to maintaining the integrity of your backup infrastructure.