CVE-2023-40931: Nagios XI SQL Injection Vulnerability

CVE-2023-40931 Overview

CVE-2023-40931 is a SQL injection vulnerability affecting Nagios XI, a widely deployed enterprise network monitoring platform. The vulnerability exists in the banner_message-ajaxhelper.php component, allowing authenticated attackers to execute arbitrary SQL commands through manipulation of the ID parameter in POST requests. This flaw enables unauthorized access to sensitive database information, potentially exposing critical infrastructure monitoring data.

Critical Impact

Authenticated attackers can extract sensitive data from the Nagios XI database, including configuration details, user credentials, and monitored host information through SQL injection attacks.

Affected Products

• Nagios XI version 5.11.0
• Nagios XI version 5.11.1
• All Nagios XI versions between 5.11.0 and 5.11.1 (inclusive)

Discovery Timeline

• 2023-09-19 - CVE-2023-40931 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-40931

Vulnerability Analysis

This SQL injection vulnerability (CWE-89) resides in the Nagios XI administrative interface, specifically within the /nagiosxi/admin/banner_message-ajaxhelper.php endpoint. The vulnerability occurs due to improper sanitization of the ID parameter when processing POST requests. An authenticated attacker with low-privilege access to the Nagios XI web interface can craft malicious SQL statements that are directly incorporated into database queries without adequate validation or parameterization.

The attack can be executed remotely over the network without requiring user interaction beyond the initial authentication. Due to the nature of SQL injection, successful exploitation could allow attackers to read sensitive information from the underlying database, including configuration data, stored credentials, and monitoring infrastructure details. The vulnerability's extremely high EPSS score of 88.305% (99.476th percentile) indicates a significant likelihood of exploitation in the wild.

Root Cause

The root cause of CVE-2023-40931 is insufficient input validation and the absence of parameterized queries in the banner_message-ajaxhelper.php file. The ID parameter from user-supplied POST data is directly concatenated into SQL queries without proper sanitization, escaping, or the use of prepared statements. This classic SQL injection pattern allows attackers to break out of the intended query structure and inject malicious SQL commands.

Attack Vector

The attack vector is network-based, requiring the attacker to have authenticated access to the Nagios XI web interface. The exploitation path follows this sequence:

1. The attacker authenticates to the Nagios XI web interface with valid (potentially low-privilege) credentials
2. The attacker crafts a malicious POST request to /nagiosxi/admin/banner_message-ajaxhelper.php
3. The ID parameter in the POST body contains SQL injection payload
4. The backend PHP code incorporates the malicious input directly into a SQL query
5. The database executes the injected SQL commands, returning unauthorized data to the attacker

The vulnerability allows for data exfiltration from the Nagios XI database. While the vulnerability requires authentication, the high EPSS percentile suggests that organizations with exposed Nagios XI instances should treat this as a high-priority remediation item. For detailed technical analysis, refer to the Outpost24 Blog on Nagios XI Vulnerabilities.

Detection Methods for CVE-2023-40931

Indicators of Compromise

• Unusual or malformed POST requests to /nagiosxi/admin/banner_message-ajaxhelper.php containing SQL syntax in the ID parameter
• Database query logs showing unexpected UNION SELECT, OR 1=1, or other SQL injection patterns
• Anomalous database access patterns or data extraction attempts from authenticated sessions
• Web application firewall alerts for SQL injection attempts against Nagios XI endpoints

Detection Strategies

• Deploy web application firewall (WAF) rules to detect and block SQL injection patterns targeting Nagios XI administrative endpoints
• Enable detailed access logging for the Nagios XI web application and monitor for suspicious POST requests to banner_message-ajaxhelper.php
• Implement database activity monitoring to identify unauthorized query execution patterns or bulk data extraction
• Configure SIEM rules to correlate authentication events with subsequent suspicious administrative endpoint access

Monitoring Recommendations

• Monitor HTTP access logs for POST requests to /nagiosxi/admin/banner_message-ajaxhelper.php with unusual parameter lengths or SQL keywords
• Implement real-time alerting for database errors that may indicate failed SQL injection attempts
• Track user session activity to identify authenticated users accessing administrative AJAX helper endpoints abnormally
• Review audit logs for data export or configuration access following banner message AJAX interactions

How to Mitigate CVE-2023-40931

Immediate Actions Required

• Upgrade Nagios XI to a version newer than 5.11.1 that contains the security patch for this vulnerability
• Restrict network access to the Nagios XI administrative interface to trusted IP addresses only
• Review user accounts and remove unnecessary administrative privileges to limit the attack surface
• Implement web application firewall rules to block SQL injection payloads targeting Nagios XI endpoints

Patch Information

Nagios has released security updates to address CVE-2023-40931. Organizations should upgrade to the latest available version of Nagios XI beyond version 5.11.1. Consult the Nagios Security Products Overview for official patch information and download links. Apply patches during a scheduled maintenance window and verify functionality of monitoring operations post-upgrade.

Workarounds

• Implement network segmentation to restrict access to Nagios XI administrative interfaces from untrusted networks
• Deploy a web application firewall (WAF) with SQL injection detection rules in front of the Nagios XI instance
• Enforce strict authentication policies and multi-factor authentication for all Nagios XI users
• Monitor and audit all access to administrative endpoints until patching can be completed

# Example: Restrict access to Nagios XI admin interface via iptables
# Allow only trusted admin networks to access the web interface
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP

# Example: Apache configuration to restrict admin endpoint access
# Add to Nagios XI Apache configuration
<Location "/nagiosxi/admin/">
    Require ip 10.0.0.0/24
</Location>