Nagios XI Privilege Escalation Remote Code Execution Vulnerability (CVE-2019-15949) Analysis and Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTNagios XI versions prior to 5.6.6
An authenticated attacker with admin web privileges or local 'nagios' user access can abuse passwordless sudo configurations to execute arbitrary commands as root
Immediately upgrade Nagios XI to version 5.6.6 or higher, and restrict write permissions on the check_plugin executable
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
The recommended remediation is to upgrade Nagios XI to version 5.6.6 or later. Run the following commands on your Nagios XI server to perform the upgrade:
# Download and run the official Nagios XI upgrade script
cd /tmp
wget https://assets.nagios.com/downloads/nagiosxi/xi-latest.tar.gz
tar xzf xi-latest.tar.gz
cd nagiosxi
./upgrade2. Temporary Workaround & Hardening Configuration
If an immediate upgrade is not feasible, mitigate the risk by changing the ownership of check_plugin to root and removing write permissions for the nagios user.
# Change ownership of check_plugin to root to prevent modification by the nagios user
chown root:root /usr/local/nagiosvm/libexec/check_plugin
chmod 755 /usr/local/nagiosvm/libexec/check_plugin
# Review sudoers configuration for getprofile.sh
# Use visudo to inspect and restrict the following entry if necessary:
# nagios ALL = NOPASSWD: /usr/local/nagiosxi/scripts/components/getprofile.sh3. Log Audit & IoC Verification Commands
Use the following commands to check your current Nagios XI version and audit the integrity of the check_plugin file:
# 1. Verify the installed Nagios XI version
grep 'product_version' /usr/local/nagiosxi/html/config.inc.php
# 2. Check ownership and modification time of check_plugin
ls -la /usr/local/nagiosvm/libexec/check_plugin
# 3. Audit web server logs for profile download requests
grep 'profile.php?cmd=download' /var/log/httpd/access_log /var/log/apache2/access.log 2>/dev/nullBlock Exploits Instantly with Managed Virtual Patching Rules
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability exists within the system profile download functionality (profile.php?cmd=download) of Nagios XI. When a profile download is requested, the web application executes the getprofile.sh script. This script is configured in /etc/sudoers to run with root privileges without requiring a password. However, getprofile.sh internally invokes an executable named check_plugin, which is insecurely owned by the non-privileged nagios user, creating a privilege escalation vector.
2. Exploitation Mechanics & Attack Scenario
An attacker who has obtained administrative access to the Nagios XI web interface or local access as the nagios user can exploit this flaw:
- The attacker modifies the
check_pluginexecutable (which is writable by thenagiosuser) to include malicious payload commands. - The attacker triggers the system profile download via the web interface (
profile.php?cmd=download). - The backend executes
sudo getprofile.shas root. - During execution,
getprofile.shruns the compromisedcheck_pluginbinary, resulting in the execution of the attacker's payload with full root privileges.
3. Infrastructure & Business Impact
Nagios XI is a critical infrastructure monitoring platform. Successful exploitation of this vulnerability grants the attacker complete control (root access) over the monitoring server. This allows attackers to harvest credentials of monitored assets, pivot into internal networks, or manipulate monitoring data to conceal further malicious activities, posing a severe threat to organizational security and business continuity.
Official Vendor Advisories & References
Nagios XI before 5.6.6 allows remote command execution as root. The exploit requires access to the server as the nagios user, or access as the admin user via the web interface. The getprofile.sh script, invoked by downloading a system profile (profile.php?cmd=download), is executed as root via a passwordless sudo entry; the script executes check_plugin, which is owned by the nagios user. A user logged into Nagios XI with permissions to modify plugins, or the nagios user on the server, can modify the check_plugin executable and insert malicious commands to execute as root.
Frequently Asked SecOps Questions (CVE-2019-15949)
FAQQ1. How critical is CVE-2019-15949 and is it actively exploited in the wild?
CVE-2019-15949 is rated CVSS 8.8 (HIGH) with a 30-day EPSS exploitation probability of 77.0%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2019-15949?
Primary impacted vendors include nagios across nagios_xi. Scope summary: All Nagios XI versions prior to 5.6.6 (Listed in CISA KEV, EPSS Score: 0.7704)
Q3. What temporary mitigations or workarounds exist for CVE-2019-15949 before patching?
[Mitigation] Immediately upgrade Nagios XI to version 5.6.6 or higher, and restrict write permissions on the check_plugin executable Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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