Nagios XI 5.7.5 Remote OS Command Injection Vulnerability (CVE-2021-25296) Security Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTNagios XI version 5.7.5
Authenticated attackers can execute arbitrary OS commands on the Nagios XI server via a single crafted HTTP request, leading to complete system compromise.
Immediately upgrade Nagios XI to the latest secure version (5.8.0 or higher) and restrict access to the web console.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Upgrade Nagios XI to the latest secure release (5.8.0 or higher) using the official upgrade script.
# Log in to the Nagios XI server as root and run the 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 patching cannot be applied immediately, disable the vulnerable wizard script and restrict network access to the Nagios XI console.
# Remove execution permissions from the vulnerable PHP script
chmod 000 /usr/local/nagiosxi/html/includes/configwizards/windowswmi/windowswmi.inc.php
# Restrict access to the Nagios XI web interface via Apache configuration
# Edit /etc/httpd/conf.d/nagiosxi.conf to allow only trusted IP ranges
# systemctl restart httpd3. Log Audit & IoC Verification Commands
Inspect Apache access logs for suspicious requests targeting the vulnerable script containing shell metacharacters.
# Search Apache access logs for suspicious requests to windowswmi.inc.php
grep -i 'windowswmi.inc.php' /var/log/httpd/access_log | grep -E '(%3b|%26|%7c|;|\&|\|)'
# Verify the currently installed Nagios XI version
cat /usr/local/nagiosxi/var/xiversionBlock Exploits Instantly with Managed Virtual Patching Rules
Can't patch production immediately? Deploy managed WAF rules at the edge to intercept RCE, SQLi, and deserialization payloads before they hit your origin server.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-25296) is an OS command injection flaw in Nagios XI, a widely used IT infrastructure monitoring solution. The root cause resides in the /usr/local/nagiosxi/html/includes/configwizards/windowswmi/windowswmi.inc.php script. The application fails to properly sanitize and validate authenticated user-controlled input before passing it to system shell execution functions.
2. Exploitation Mechanics & Attack Scenario
An attacker with valid credentials (even low-privileged ones) can exploit this vulnerability by sending a single HTTP POST request to the Windows WMI configuration wizard. By injecting shell metacharacters (such as ;, &, or |) followed by malicious commands into the vulnerable parameters, the attacker forces the underlying PHP script to execute arbitrary OS commands with the privileges of the web server or Nagios process (typically nagios or apache).
3. Infrastructure & Business Impact
With a CVSS 3.1 score of 8.8 (High) and its inclusion in the CISA KEV (Known Exploited Vulnerabilities) catalog, this vulnerability poses a severe threat. Successful exploitation allows attackers to gain a foothold on the monitoring server, potentially exposing sensitive infrastructure credentials and enabling lateral movement across the internal network.
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/windowswmi/windowswmi.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-2021-25296)
FAQQ1. How critical is CVE-2021-25296 and is it actively exploited in the wild?
CVE-2021-25296 is rated CVSS 8.8 (HIGH) with a 30-day EPSS exploitation probability of 71.9%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-25296?
Primary impacted vendors include nagios across nagios_xi. Scope summary: Nagios XI version 5.7.5 with the Windows WMI config wizard enabled
Q3. What temporary mitigations or workarounds exist for CVE-2021-25296 before patching?
[Mitigation] Immediately upgrade Nagios XI to the latest secure version (5.8.0 or higher) and restrict access to the web console. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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