CVE-2016-1561 in ExaGrid
Summary
by MITRE
ExaGrid appliances with firmware before 4.8 P26 have a default SSH public key in the authorized_keys file for root, which allows remote attackers to obtain SSH access by leveraging knowledge of a private key from another installation or a firmware image.
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Analysis
by VulDB Data Team • 11/30/2024
The vulnerability described in CVE-2016-1561 represents a critical security flaw in ExaGrid backup appliances that affects firmware versions prior to 4.8 P26. This issue stems from a hardcoded SSH public key embedded within the authorized_keys file for the root user account, creating a persistent backdoor mechanism that significantly compromises the device's security posture. The flaw is particularly dangerous because it allows remote attackers to establish unauthorized SSH sessions without requiring legitimate credentials or authentication mechanisms.
The technical implementation of this vulnerability involves a hardcoded public key that remains consistent across multiple ExaGrid appliances, making it exploitable through knowledge of the corresponding private key from any other affected installation or firmware image. This design flaw violates fundamental security principles of credential management and authentication, as it creates a universal access vector that bypasses normal authentication procedures. The vulnerability specifically affects the SSH daemon configuration where the authorized_keys file contains a predetermined public key that grants root access, essentially creating a shared secret across all affected devices.
From an operational impact perspective, this vulnerability enables attackers to gain complete administrative control over affected ExaGrid appliances, potentially leading to data exfiltration, system compromise, and disruption of backup operations. The attack surface is particularly concerning because it allows remote exploitation without requiring physical access or knowledge of legitimate user credentials. Organizations utilizing these appliances face significant risk of unauthorized access to their backup infrastructure, which could result in catastrophic data loss or system compromise. The vulnerability's persistence across firmware versions makes it particularly challenging to remediate without comprehensive device updates.
Security professionals should consider this vulnerability in relation to CWE-310, which addresses cryptographic flaws and improper key management practices. The flaw demonstrates poor implementation of secure key distribution and management, violating the principle of least privilege and creating a persistent security risk. Organizations should implement immediate mitigations including firmware updates to version 4.8 P26 or later, which would remove the hardcoded public key from the authorized_keys file. Additionally, network segmentation and monitoring of SSH access attempts should be implemented to detect potential exploitation attempts. The vulnerability also aligns with ATT&CK technique T1021.004, which covers SSH and Telnet protocols, highlighting the need for proper access control and monitoring of remote administration services.