CVE-2020-28902 in Fusion
Summary
by MITRE • 05/24/2021
Command Injection in Nagios Fusion 4.1.8 and earlier allows Privilege Escalation from apache to root in cmd_subsys.php.
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Analysis
by VulDB Data Team • 05/27/2021
The vulnerability identified as CVE-2020-28902 represents a critical command injection flaw within Nagios Fusion version 4.1.8 and earlier installations. This vulnerability exists in the cmd_subsys.php component of the web-based monitoring platform, which is commonly used for network and system monitoring in enterprise environments. The flaw allows an attacker with limited privileges to execute arbitrary commands on the underlying operating system, potentially leading to complete system compromise. The vulnerability is particularly concerning because it enables privilege escalation from the apache user account to the root account, which represents the highest level of system access possible.
The technical implementation of this command injection vulnerability stems from inadequate input validation and sanitization within the cmd_subsys.php script. When the application processes user-supplied data through web forms or API endpoints, it fails to properly escape or validate command parameters before incorporating them into system execution calls. This allows attackers to inject malicious commands that are subsequently executed with the privileges of the web server process, which in many configurations runs as the apache user. The vulnerability aligns with CWE-77, which categorizes command injection flaws as weaknesses that occur when an application passes untrusted data to an operating system command without proper validation or sanitization. The specific nature of this flaw enables attackers to bypass authentication mechanisms and escalate their privileges through the web interface.
The operational impact of this vulnerability extends beyond simple command execution, as it provides attackers with complete control over the target system. Once an attacker successfully exploits this vulnerability, they can establish persistent access, extract sensitive data, modify system configurations, or deploy additional malicious software. The privilege escalation to root level means that attackers can manipulate system files, create new user accounts, disable security controls, and potentially compromise the entire network infrastructure. This vulnerability directly maps to ATT&CK technique T1059.001, which covers command and scripting interpreter, and T1548.001, which involves abuse of system permissions. The attack surface is particularly wide in environments where Nagios Fusion is deployed, as it often serves as a central monitoring point for critical infrastructure components.
Organizations should immediately implement multiple layers of defense to protect against exploitation of this vulnerability. The primary mitigation strategy involves applying the vendor-provided security patch that addresses the input validation issues in cmd_subsys.php. Additionally, network segmentation should be implemented to limit access to the Nagios Fusion web interface to only authorized personnel and systems. Input validation should be strengthened through the implementation of proper parameter sanitization and the use of allowlists for command execution. Security monitoring should be enhanced to detect unusual command execution patterns, and access controls should be reviewed to ensure that only necessary users have access to the vulnerable functionality. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other components of the monitoring infrastructure, as this type of flaw often indicates broader security weaknesses in the application architecture. The vulnerability demonstrates the critical importance of secure coding practices and proper input validation in preventing privilege escalation attacks that can lead to complete system compromise.