CVE-2016-15049 in Log Server
Summary
by MITRE • 10/31/2025
Nagios Log Server versions prior to 1.4.2 are vulnerable to cross-site scripting (XSS) in the Dashboards section when rendering log entries in the Logs table. Untrusted log content was not safely encoded for the output context, allowing attacker-controlled data present in logs to execute script in the victim’s browser within the application origin.
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Analysis
by VulDB Data Team • 10/31/2025
The vulnerability identified as CVE-2016-15049 affects Nagios Log Server versions earlier than 1.4.2 and represents a critical cross-site scripting flaw within the Dashboards functionality. This security weakness specifically manifests in the Logs table component where log entries are rendered, creating an environment where malicious scripts can be executed in the context of a victim's browser session. The vulnerability stems from inadequate input sanitization and output encoding practices within the application's rendering pipeline, allowing attackers to inject malicious code that persists in the log data and executes when other users view the affected dashboard components.
The technical implementation of this vulnerability involves the failure to properly encode untrusted data before incorporating it into the web application's output context. When log entries containing malicious script content are processed and displayed in the Logs table, the application does not adequately escape or encode special characters that could be interpreted as executable code by web browsers. This creates a persistent cross-site scripting vector where the attacker's malicious payload becomes part of the logged content and executes whenever legitimate users access the dashboard. The vulnerability is particularly dangerous because it leverages the legitimate trust relationship between the application and its users, executing code within the application's origin domain and bypassing typical browser security restrictions.
From an operational perspective, this vulnerability enables attackers to perform a range of malicious activities including session hijacking, credential theft, data exfiltration, and privilege escalation within the application context. The impact extends beyond simple script execution as attackers can leverage the persistent nature of log data to maintain long-term access to the system. Since the vulnerability affects the dashboard functionality, it could potentially allow attackers to view sensitive log information, manipulate dashboard configurations, or even escalate privileges if the application grants administrative capabilities through the dashboard interface. The attack requires minimal prerequisites as it exploits the natural flow of log data processing and display, making it particularly stealthy and difficult to detect.
The vulnerability aligns with CWE-79 which defines cross-site scripting as a weakness where untrusted data is incorporated into web pages without proper validation or encoding, and it maps to ATT&CK technique T1566.001 for initial access through malicious web content. Organizations should implement immediate mitigations including upgrading to Nagios Log Server version 1.4.2 or later, which contains proper output encoding mechanisms for log data rendering. Additional protective measures include implementing Content Security Policy headers, conducting regular input validation on log data, and establishing monitoring for unusual dashboard access patterns that might indicate exploitation attempts. Security teams should also consider implementing web application firewalls to detect and block common XSS attack patterns targeting the affected dashboard components.