CVE-2020-28906 in Fusion
Summary
by MITRE • 05/24/2021
Incorrect File Permissions in Nagios XI 5.7.5 and earlier and Nagios Fusion 4.1.8 and earlier allows for Privilege Escalation to root. Low-privileged users are able to modify files that are included (aka sourced) by scripts executed by root.
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Analysis
by VulDB Data Team • 05/27/2021
The vulnerability identified as CVE-2020-28906 represents a critical privilege escalation flaw affecting Nagios XI versions 5.7.5 and earlier, as well as Nagios Fusion versions 4.1.8 and earlier. This issue stems from improper file permissions that allow low-privileged users to manipulate files which are subsequently included or sourced by root-executed scripts. The flaw fundamentally compromises the security model of these monitoring platforms by creating an attack vector where unprivileged users can elevate their privileges to the highest system level. The vulnerability is particularly dangerous because it leverages the trust model inherent in script inclusion mechanisms, where files sourced by privileged processes are not properly protected against modification by unauthorized users.
The technical implementation of this vulnerability involves a misconfiguration in file permission settings that govern access to critical system files within the Nagios monitoring environment. When the system processes scripts that include or source other files, it does so with elevated privileges typically belonging to the root user. However, due to inadequate file permissions, users with lower privileges can modify these included files, effectively allowing them to inject malicious code or alter system behavior. This creates a classic privilege escalation scenario where user-level access can be leveraged to gain root-level control over the system. The flaw operates through the principle of insecure file inclusion, where the system fails to validate the integrity or access permissions of files that are dynamically included during script execution.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the security posture of systems relying on these monitoring platforms. Attackers exploiting this vulnerability can gain complete control over the affected systems, potentially leading to data breaches, system compromise, or further lateral movement within network environments. The low privilege requirements for exploitation make this vulnerability particularly attractive to attackers, as it requires minimal access to begin the attack chain. Organizations using these affected versions face significant risk of unauthorized access and system compromise, especially in environments where monitoring systems are critical infrastructure components. The vulnerability also demonstrates poor security hygiene in file access control mechanisms and highlights the importance of principle of least privilege in system design.
Mitigation strategies for this vulnerability should focus on immediate remediation through version updates to patched releases of Nagios XI and Nagios Fusion. Organizations must also implement proper file permission controls to ensure that files included by root-executed scripts maintain appropriate access restrictions. System administrators should conduct thorough audits of file permissions and access controls within Nagios installations, particularly focusing on files that are sourced by privileged processes. The implementation of file integrity monitoring solutions can help detect unauthorized modifications to critical system files. Additionally, organizations should review their overall security configuration management practices and ensure that security updates are applied promptly. This vulnerability aligns with CWE-276, which addresses incorrect permissions for critical resources, and maps to ATT&CK technique T1068, privilege escalation through insecure file permissions. Regular security assessments and vulnerability scanning should be implemented to identify similar issues in other system components and prevent future exploitation attempts.