CVE-2021-43043: 
Kaseya Unitrends Agent vulnerability analysis and mitigation

An issue was discovered in Kaseya Unitrends Backup Appliance before version 10.5.5, identified as CVE-2021-43043. The vulnerability allowed the apache user to read arbitrary files such as /etc/shadow by abusing an insecure Sudo rule. This vulnerability was disclosed in December 2021 and was assigned a CVSS v3.1 base score of 7.2 (High) (NVD, Kaseya Advisory).

The vulnerability stems from an insecure Sudo rule configuration that granted the apache user excessive privileges to read arbitrary files on the system. This misconfiguration specifically allowed access to sensitive system files, including the /etc/shadow file which contains password hashes for system accounts. The vulnerability was rated with a CVSS v3.1 Vector of CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N, indicating network accessibility, low attack complexity, and high impact on confidentiality (NVD).

The vulnerability allows unauthorized access to sensitive system files, particularly the /etc/shadow file, which contains password hashes for all system users. This exposure could lead to offline password cracking attempts and potentially unauthorized system access if the password hashes are successfully cracked (Kaseya Advisory).

The vulnerability requires low attack complexity and can be exploited by an attacker with apache user privileges. Detailed exploit information has been published, demonstrating how this vulnerability can be chained with other issues to achieve privilege escalation (CyberOne Blog).

Users should immediately update to Unitrends software version 10.5.5 or later to address this vulnerability. This update corrects the insecure Sudo rule configuration that allowed the unauthorized file access (Kaseya Advisory).