CVE-2023-40932 in Nagios
Summary
by MITRE • 09/20/2023
A Cross-site scripting (XSS) vulnerability in Nagios XI version 5.11.1 and below allows authenticated attackers with access to the custom logo component to inject arbitrary javascript or HTML via the alt-text field. This affects all pages containing the navbar including the login page which means the attacker is able to to steal plaintext credentials.
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Analysis
by VulDB Data Team • 01/30/2026
This cross-site scripting vulnerability exists within Nagios XI version 5.11.1 and earlier releases, representing a critical security flaw that enables authenticated attackers to execute malicious scripts through the custom logo component. The vulnerability specifically targets the alt-text field within the logo configuration, allowing an attacker with sufficient privileges to inject arbitrary javascript or html code. This flaw falls under CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental weakness in web application security where user-supplied data is not properly sanitized before being rendered in web pages. The attack vector requires authentication and access to the custom logo component, making it a privilege escalation vulnerability that can be exploited by users with administrative or configuration access rights.
The operational impact of this vulnerability extends far beyond simple script injection, as it affects all pages containing the navbar including the login page itself. This critical design flaw means that when an attacker successfully injects malicious code through the alt-text field, the payload executes in the context of any user who visits pages with the affected navbar component. The most severe consequence is the ability to steal plaintext credentials, as the attacker can capture login information from the vulnerable login page and other authenticated sections of the application. This represents a direct violation of the principle of least privilege and creates a persistent threat vector that can compromise the entire Nagios XI environment.
The attack chain begins with an authenticated user accessing the custom logo configuration interface, where they can manipulate the alt-text field to include malicious javascript code. When the modified logo is rendered on any page containing the navbar, the injected script executes in the victim's browser context, potentially capturing session cookies, redirecting users to malicious sites, or performing actions on behalf of the authenticated user. This vulnerability demonstrates the dangerous combination of insufficient input validation and the broad scope of the navbar component, which serves as a critical navigation element across the entire application. The fact that the login page is affected makes this particularly dangerous as it can be used to harvest credentials from any user attempting to authenticate, creating a persistent backdoor into the monitoring system.
Mitigation strategies should focus on immediate input sanitization and output encoding for all user-supplied content within the logo configuration component. Implementing proper content security policies and sanitizing all alt-text field inputs through libraries designed to prevent XSS attacks would address the root cause. Organizations should also consider implementing multi-factor authentication and monitoring for unusual access patterns in the custom logo configuration area. The vulnerability highlights the importance of following the OWASP Top Ten security principles and demonstrates how seemingly minor configuration components can create major security risks. Regular security assessments and proper input validation should be enforced across all web application components, particularly those that are frequently modified by users with administrative privileges. Additionally, implementing proper access controls and audit logging for configuration changes can help detect and prevent exploitation attempts.