CVE-2020-36858
📋 TL;DR
This cross-site scripting (XSS) vulnerability in Nagios Log Server allows attackers to inject malicious scripts into web pages when users interact with Create User, Edit User, or Manage Host Lists functions. If exploited, these scripts execute in victims' browsers, potentially stealing credentials, session tokens, or performing unauthorized actions. Organizations using Nagios Log Server versions before 2.1.6 are affected.
💻 Affected Systems
- Nagios Log Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attacker gains administrative access to Nagios Log Server, steals all monitoring data, compromises credentials for integrated systems, and uses the server as a pivot point to attack internal networks.
Likely Case
Attacker steals session cookies or authentication tokens to impersonate legitimate users, modifies monitoring configurations to hide malicious activity, or redirects users to phishing sites.
If Mitigated
Script execution is blocked by browser security features, or the attack only affects users with limited permissions, causing minimal data exposure.
🎯 Exploit Status
Exploitation requires authenticated access to the web interface and victim interaction with injected pages.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.1.6 and later
Vendor Advisory: https://www.nagios.com/changelog/nagios-log-server-2024r1/
Restart Required: No
Instructions:
1. Backup current configuration. 2. Download Nagios Log Server 2.1.6 or later from Nagios website. 3. Follow upgrade instructions in documentation. 4. Verify upgrade completed successfully.
🔧 Temporary Workarounds
Input Validation Enhancement
allImplement additional input validation and output encoding for user-supplied data in web interface forms.
Content Security Policy
allImplement strict Content Security Policy headers to restrict script execution sources.
🧯 If You Can't Patch
- Restrict access to Nagios Log Server web interface to trusted users only using network segmentation and firewall rules.
- Implement web application firewall (WAF) rules to detect and block XSS payloads in HTTP requests.
🔍 How to Verify
Check if Vulnerable:
Check Nagios Log Server version via web interface dashboard or command line: cat /usr/local/nagioslogserver/version.txtCheck Version:
cat /usr/local/nagioslogserver/version.txtVerify Fix Applied:
Verify version is 2.1.6 or higher and test vulnerable pages (Create User, Edit User, Manage Host Lists) with basic XSS payloads to confirm sanitization.📡 Detection & Monitoring
Log Indicators:
- Unusual JavaScript or HTML patterns in user input fields
- Multiple failed login attempts followed by successful login from same IP
- Unexpected modifications to user accounts or host lists
Network Indicators:
- HTTP requests containing script tags or JavaScript code in form parameters
- Unusual outbound connections from Nagios server to external domains
SIEM Query:
source="nagios_log_server" AND (http_request="*<script>*" OR http_request="*javascript:*" OR http_request="*onerror=*" OR http_request="*onload=*")