CVE-2020-36858 in Log Server
Summary
by MITRE • 10/31/2025
Nagios Log Server versions prior to 2.1.6 contain cross-site scripting (XSS) vulnerabilities via the web interface on the Create User, Edit User, and Manage Host Lists pages. Insufficient validation or escaping of user-supplied input may allow an attacker to inject and execute arbitrary script in the context of a victim's browser.
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Analysis
by VulDB Data Team • 10/31/2025
The vulnerability identified as CVE-2020-36858 affects Nagios Log Server versions prior to 2.1.6 and represents a critical cross-site scripting flaw that undermines the security posture of the web-based interface. This vulnerability specifically targets three key administrative pages including Create User, Edit User, and Manage Host Lists, where user-supplied input is not adequately validated or escaped before being rendered in the browser context. The flaw stems from insufficient input sanitization mechanisms that fail to properly encode or filter malicious script content submitted by users, creating an exploitable condition that allows attackers to inject arbitrary JavaScript code into the application's web interface.
The technical execution of this vulnerability follows the standard XSS attack pattern where an attacker crafts malicious input containing script payloads that get stored or reflected within the application's user interface. When legitimate users access the affected pages, their browsers execute the injected scripts within the context of their authenticated sessions, potentially enabling attackers to steal session cookies, perform unauthorized actions, or redirect users to malicious domains. This vulnerability directly maps to CWE-79 which defines Cross-Site Scripting as a weakness where applications fail to properly validate or escape user-supplied data before including it in dynamically generated web pages. The attack vector operates through the web interface, making it particularly dangerous as it can be exploited by both authenticated and unauthenticated users depending on the specific page and access controls in place.
The operational impact of this vulnerability extends beyond simple script execution as it fundamentally compromises the integrity of the user session and the application's security model. An attacker who successfully exploits this vulnerability can potentially escalate privileges, access sensitive user data, or manipulate the application's configuration through the administrative interfaces. The affected pages represent critical administrative functions that control user management and host list configurations, making them prime targets for exploitation. According to ATT&CK framework category T1059.007, this vulnerability enables command and control activities through script injection, while T1548.002 addresses privilege escalation opportunities that may arise from compromised administrative interfaces. The vulnerability also aligns with T1190 which covers exploitation of web application vulnerabilities, particularly those involving input validation failures in web forms.
Mitigation strategies for CVE-2020-36858 require immediate implementation of the vendor-provided patch for Nagios Log Server version 2.1.6 or later, which addresses the insufficient input validation mechanisms. Organizations should implement comprehensive input validation and output encoding measures across all user-facing web interfaces, particularly focusing on the administrative pages mentioned in the vulnerability description. The remediation process should include validating all user-supplied input against strict whitelists and implementing proper HTML escaping for dynamic content rendering. Security teams should also consider implementing web application firewalls to detect and prevent XSS attack patterns, while conducting thorough security assessments to identify similar vulnerabilities in other web applications within the environment. Additionally, user education regarding the risks of clicking suspicious links or submitting untrusted input remains crucial in defending against exploitation attempts that leverage this class of vulnerability.