CVE-2018-18249 in Web 2
Summary
by MITRE
Icinga Web 2 before 2.6.2 allows injection of PHP ini-file directives via vectors involving environment variables as the channel to send information to the attacker, such as a name=${PATH}_${APACHE_RUN_DIR}_${APACHE_RUN_USER} parameter to /icingaweb2/navigation/add or /icingaweb2/dashboard/new-dashlet.
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Analysis
by VulDB Data Team • 04/21/2020
This vulnerability exists in Icinga Web 2 versions prior to 2.6.2 and represents a critical security flaw that allows remote attackers to inject PHP configuration directives through environment variables. The vulnerability manifests when the application processes user-supplied parameters that are subsequently used to construct PHP ini settings, creating a pathway for arbitrary code execution and system compromise. The specific attack vector involves environment variables such as PATH, APACHE_RUN_DIR, and APACHE_RUN_USER which are manipulated through parameters like name=${PATH}${APACHE_RUN_DIR}${APACHE_RUN_USER} to be passed to endpoints such as /icingaweb2/navigation/add or /icingaweb2/dashboard/new-dashlet. This vulnerability falls under the CWE-15 category of External Control of System or Configuration Setting, where an application accepts input from untrusted sources that can alter system configuration parameters.
The technical implementation of this vulnerability exploits the application's improper handling of user-controllable input within configuration contexts. When attackers craft malicious parameters containing environment variable references, these variables are expanded and injected directly into PHP configuration directives without proper sanitization or validation. This creates a scenario where an attacker can manipulate critical PHP settings such as open_basedir, allow_url_include, or other security-relevant parameters that can subsequently be leveraged to bypass security restrictions and execute arbitrary PHP code. The vulnerability is particularly dangerous because it operates at the system configuration level rather than application level, potentially allowing attackers to modify fundamental PHP runtime behaviors that control file access, remote code execution capabilities, and other critical security mechanisms.
The operational impact of this vulnerability extends far beyond simple information disclosure, as it can lead to complete system compromise and unauthorized access to sensitive monitoring data. Attackers who successfully exploit this vulnerability can manipulate the underlying PHP configuration to disable security features, enable remote code execution, or gain elevated privileges within the Icinga Web 2 environment. This represents a significant risk to organizations that rely on Icinga for infrastructure monitoring, as compromised monitoring systems can provide attackers with visibility into critical network components and potentially serve as a stepping stone for broader network infiltration. The attack can be executed remotely without authentication, making it particularly dangerous for publicly accessible monitoring systems. According to ATT&CK framework, this vulnerability maps to T1059.007 for PHP-based command execution and T1068 for local privilege escalation through configuration manipulation.
Mitigation strategies should focus on immediate patching of Icinga Web 2 to version 2.6.2 or later, which includes proper input validation and sanitization for environment variable references. Organizations should implement network segmentation to limit access to Icinga Web 2 interfaces and enforce strict access controls through authentication mechanisms. Additional protective measures include monitoring for unusual parameter patterns in web application logs, implementing web application firewalls to detect and block malicious injection attempts, and conducting regular security assessments of monitoring systems. The vulnerability highlights the importance of input validation at all levels of application processing and demonstrates the critical need for proper sanitization of environment variables when they are used in system configuration contexts. Security teams should also consider implementing automated patch management processes to ensure timely deployment of security updates and maintain comprehensive monitoring of system configuration changes that could indicate exploitation attempts.