Nagios XI 5.7.5 Remote OS Command Injection Vulnerability (CVE-2021-25298) Security Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTNagios XI version 5.7.5
An authenticated attacker can execute arbitrary OS commands on the Nagios XI server via a single crafted HTTP request, potentially leading to full system compromise.
Immediately upgrade Nagios XI to a patched version (5.8.0 or higher), or disable/restrict access to the vulnerable configuration wizard.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Upgrade Nagios XI to the latest stable version (5.8.0 or higher) where this vulnerability has been resolved. Use the following commands to download and run the official upgrade script:
# Access the Nagios XI server as root and perform the upgrade
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, temporarily disable the vulnerable cloud-vm configuration wizard by moving it out of the web directory, and restrict access to the Nagios XI console.
# Backup and remove the vulnerable cloud-vm wizard directory
mv /usr/local/nagiosxi/html/includes/configwizards/cloud-vm /usr/local/nagiosxi/html/includes/configwizards/cloud-vm.bak
# Restrict access to the Nagios XI web interface to trusted IP ranges in Apache configuration
# Add the following directive to your Apache configuration file (e.g., /etc/httpd/conf.d/nagiosxi.conf)
<Directory '/usr/local/nagiosxi/html'>
Require ip 10.0.0.0/8 192.168.0.0/16
</Directory>3. Log Audit & IoC Verification Commands
Inspect the web server access logs for suspicious requests targeting the cloud-vm wizard containing shell metacharacters.
# Search Apache access logs for cloud-vm wizard execution and command injection attempts
grep -i 'cloud-vm' /var/log/httpd/access_log | grep -E '(%3B|%26|%7C|;|\&|\|)'
# Verify the currently installed Nagios XI version
grep 'product_version' /usr/local/nagiosxi/html/config.inc.phpBlock Exploits Instantly with Managed Virtual Patching Rules
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-25298) is an OS command injection flaw in the network and infrastructure monitoring solution Nagios XI version 5.7.5. The root cause lies within the /usr/local/nagiosxi/html/includes/configwizards/cloud-vm/cloud-vm.inc.php file, where user-controlled input is processed without adequate sanitization or validation before being passed directly to system shell execution functions.
2. Exploitation Mechanics & Attack Scenario
To exploit this vulnerability, an attacker must first obtain valid credentials to authenticate to the Nagios XI web interface. Once authenticated, the attacker can send a single HTTP request targeting the cloud-vm configuration wizard, embedding shell metacharacters (such as ;, &, |, or ` `) within the input parameters. The backend PHP script executes these parameters directly via system shell commands, allowing the attacker to run arbitrary OS commands with the privileges of the web server user (typically apache or nagios`).
3. Infrastructure & Business Impact
Since Nagios XI is centrally positioned to monitor critical enterprise servers, network devices, and cloud infrastructure, a compromise of this server is highly critical. Attackers can leverage this access to harvest credentials, map internal network topologies, pivot to other internal systems, or deploy ransomware. This vulnerability is actively exploited in the wild, as indicated by its inclusion in the CISA KEV list and its high EPSS score.
Official Vendor Advisories & References
Nagios XI version xi-5.7.5 is affected by OS command injection. The vulnerability exists in the file /usr/local/nagiosxi/html/includes/configwizards/cloud-vm/cloud-vm.inc.php due to improper sanitization of authenticated user-controlled input by a single HTTP request, which can lead to OS command injection on the Nagios XI server.
Frequently Asked SecOps Questions (CVE-2021-25298)
FAQQ1. How critical is CVE-2021-25298 and is it actively exploited in the wild?
CVE-2021-25298 is rated CVSS 8.8 (HIGH) with a 30-day EPSS exploitation probability of 73.6%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-25298?
Primary impacted vendors include nagios across nagios_xi. Scope summary: Nagios XI version 5.7.5 with the cloud-vm configuration wizard enabled
Q3. What temporary mitigations or workarounds exist for CVE-2021-25298 before patching?
[Mitigation] Immediately upgrade Nagios XI to a patched version (5.8.0 or higher), or disable/restrict access to the vulnerable configuration wizard. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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