CVE-2018-20171 in Nagios XI
Summary
by MITRE
An issue was discovered in Nagios XI before 5.5.8. The url parameter of rss_dashlet/magpierss/scripts/magpie_simple.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-2018-20171 represents a cross-site scripting weakness within Nagios XI monitoring platform prior to version 5.5.8. This security flaw exists in the rss_dashlet module's magpierss component, specifically in the magpie_simple.php script where the url parameter fails to undergo proper input validation or sanitization. The affected system processes user-supplied URL values without adequate filtering mechanisms, creating an avenue for malicious actors to inject arbitrary JavaScript code into the application's response. This oversight allows attackers to exploit the vulnerability through carefully crafted malicious URLs that can be passed to the vulnerable parameter, potentially executing unauthorized scripts in the context of authenticated users' browsers. The vulnerability stems from improper handling of user input within the RSS feed parsing functionality, which is commonly used for displaying external content within the Nagios XI dashboard interface.
The technical exploitation of this vulnerability follows standard XSS attack patterns where an attacker crafts a malicious URL containing JavaScript payload and delivers it to unsuspecting users through phishing emails, compromised websites, or social engineering tactics. When a victim accesses the malicious link, the vulnerable application processes the unfiltered url parameter and includes it directly in the HTTP response without proper HTML escaping or sanitization. This allows the injected JavaScript code to execute within the victim's browser context, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The vulnerability specifically falls under CWE-79 which categorizes improper neutralization of input during web page generation, and represents a classic reflected XSS vulnerability where the malicious input is immediately reflected back to the user. From an attack perspective, this flaw aligns with ATT&CK technique T1566.001 for initial access through spearphishing attachments and T1071.004 for application layer protocol usage.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to gain unauthorized access to sensitive monitoring data and system configurations within the Nagios XI environment. Since Nagios XI typically operates with elevated privileges and provides access to critical infrastructure monitoring information, successful exploitation could lead to comprehensive exposure of network assets, system vulnerabilities, and operational details. The attack surface is particularly concerning because Nagios XI interfaces are often accessible to multiple users within an organization, increasing the potential for widespread compromise. Organizations using this monitoring platform may experience unauthorized access to critical system information, potential disruption of monitoring services, and possible data exfiltration. The vulnerability's persistence in versions prior to 5.5.8 indicates a prolonged exposure period where organizations remained vulnerable to attacks targeting this specific input validation flaw.
Mitigation strategies for CVE-2018-20171 should prioritize immediate patch application to Nagios XI version 5.5.8 or later, which includes proper input sanitization for the affected url parameter. Organizations should implement comprehensive input validation and output encoding mechanisms throughout their web applications to prevent similar vulnerabilities from occurring in other components. Network segmentation and access controls should be enforced to limit exposure of the Nagios XI interface to trusted users only, reducing the attack surface available to potential adversaries. Additionally, implementing web application firewalls and content security policies can provide additional layers of protection against XSS attacks, while regular security assessments and penetration testing should be conducted to identify and remediate similar input validation weaknesses. Security monitoring should include detection of suspicious URL patterns and unusual access attempts to the affected rss_dashlet functionality, ensuring early identification of potential exploitation attempts.