CVE-2018-20172 in Nagios XI
Summary
by MITRE
An issue was discovered in Nagios XI before 5.5.8. The rss_url parameter of rss_dashlet/magpierss/scripts/magpie_slashbox.php is not filtered, resulting in an XSS vulnerability.
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Analysis
by VulDB Data Team • 04/21/2020
The vulnerability identified as CVE-2018-20172 represents a cross-site scripting flaw within Nagios XI version 5.5.7 and earlier, specifically affecting the rss_dashlet component that utilizes the magpierss library. This security weakness stems from insufficient input validation and sanitization of the rss_url parameter within the magpie_slashbox.php script, creating an avenue for malicious actors to inject arbitrary web scripts into the application's user interface. The flaw exists in the context of a web-based monitoring platform where users interact with dashlets to display RSS feeds, making the vulnerability particularly dangerous as it can be exploited through legitimate user interactions with the dashboard interface.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious URL containing script code within the rss_url parameter and persuades a victim to click on the link or view the affected dashboard. The unfiltered input gets directly embedded into the page output without proper HTML escaping or sanitization, allowing the malicious script to execute in the victim's browser context with the privileges of the logged-in user. This type of vulnerability falls under CWE-79 which specifically addresses cross-site scripting flaws, and more precisely aligns with CWE-79-2007 which describes improper neutralization of input during web output. The vulnerability demonstrates a classic injection flaw where user-controllable data flows directly into the application's output without adequate filtering mechanisms.
The operational impact of this vulnerability extends beyond simple script execution as it can enable attackers to perform session hijacking, steal user credentials, manipulate dashboard content, or redirect users to malicious websites. An attacker could potentially escalate the attack by using the compromised user session to access sensitive monitoring data, modify system configurations, or even gain unauthorized access to underlying network infrastructure that Nagios XI monitors. The vulnerability affects the integrity and confidentiality of the monitoring environment, as users may unknowingly execute malicious code while interacting with their dashboard, potentially leading to data exfiltration or further compromise of the network infrastructure. This weakness particularly impacts organizations that rely heavily on Nagios XI for critical infrastructure monitoring, as it could go undetected while attackers leverage the compromised sessions for prolonged reconnaissance activities.
Organizations should immediately upgrade to Nagios XI version 5.5.8 or later, which contains the necessary patches to address this vulnerability. Additionally, implementing proper input validation at the application level, including the use of Content Security Policy headers, can provide additional defense-in-depth measures. Network segmentation and monitoring of dashboard access patterns may help detect exploitation attempts, while user education regarding suspicious links and dashboard interactions can reduce successful social engineering attacks. Security teams should also consider implementing web application firewalls that can detect and block malicious input patterns targeting similar vulnerabilities in the magpierss library. The mitigation strategy should align with ATT&CK technique T1059.007 which covers scripting through web shell execution, as the vulnerability creates conditions where attackers can establish persistent access through malicious script injection. Regular security assessments of third-party components like magpierss should be conducted to identify similar vulnerabilities that may exist in other integrated libraries or frameworks within the monitoring ecosystem.