CVE-2023-28724: F5 Nginx Privilege Escalation Vulnerability

CVE-2023-28724 Overview

CVE-2023-28724 is an Insecure Default Configuration vulnerability affecting F5 NGINX Management Suite products. The default file permissions are set such that an authenticated attacker may be able to modify sensitive files on NGINX Instance Manager and NGINX API Connectivity Manager. This improper permission configuration (CWE-276) could allow malicious actors with local access to escalate privileges or compromise the integrity of critical configuration files.

Critical Impact

Authenticated attackers with local access can modify sensitive files on NGINX Instance Manager and NGINX API Connectivity Manager, potentially leading to unauthorized configuration changes, privilege escalation, or system compromise.

Affected Products

• F5 NGINX API Connectivity Manager
• F5 NGINX Instance Manager
• F5 NGINX Security Monitoring

Discovery Timeline

• 2023-05-03 - CVE-2023-28724 published to NVD
• 2025-04-10 - Last updated in NVD database

Technical Details for CVE-2023-28724

Vulnerability Analysis

This vulnerability stems from improper default file permissions in the NGINX Management Suite. When the suite is installed with default settings, certain sensitive configuration and system files are created with overly permissive access rights. An authenticated user with local system access can leverage these weak permissions to read or modify files they should not have access to, potentially leading to unauthorized changes to the NGINX configuration, exposure of sensitive data, or escalation of privileges within the affected system.

The local attack vector means an attacker must have some form of authenticated access to the system where NGINX Management Suite is installed. While this requirement limits the attack surface, environments with multiple users or shared access scenarios are particularly vulnerable. The vulnerability affects the confidentiality and integrity of the system without impacting availability.

Root Cause

The root cause of CVE-2023-28724 is CWE-276 (Incorrect Default Permissions). During installation or operation, NGINX Management Suite creates files with default permissions that are more permissive than necessary for the principle of least privilege. This allows authenticated users to access and potentially modify sensitive configuration files, credentials, or other critical system data that should be restricted to administrative accounts only.

Attack Vector

The attack requires local access to the system running NGINX Management Suite. An authenticated attacker would:

1. Gain local access to the target system through legitimate credentials or another vulnerability
2. Enumerate file permissions on NGINX Management Suite directories
3. Identify sensitive files with overly permissive access controls
4. Read sensitive configuration data or modify files to inject malicious configurations
5. Leverage the modified configurations for privilege escalation or persistence

The vulnerability can be exploited to modify sensitive NGINX configuration files, potentially allowing the attacker to redirect traffic, inject malicious content, or gain elevated access to the management suite functionality.

Detection Methods for CVE-2023-28724

Indicators of Compromise

• Unexpected modifications to NGINX Management Suite configuration files
• Changes to file permissions or ownership on NGINX-related directories
• Unusual user activity accessing NGINX configuration directories
• Audit log entries showing non-administrative users accessing sensitive files

Detection Strategies

• Implement file integrity monitoring (FIM) on NGINX Management Suite installation directories
• Monitor system audit logs for file access and modification events on sensitive configurations
• Deploy endpoint detection solutions to alert on suspicious file permission changes
• Regularly audit user access patterns to NGINX Management Suite components

Monitoring Recommendations

• Enable detailed file access auditing on /etc/nms/ and related NGINX Management Suite directories
• Configure SIEM alerts for unauthorized file modifications to NGINX configuration files
• Monitor for privilege escalation attempts following file permission abuse
• Implement baseline comparisons for critical configuration files

How to Mitigate CVE-2023-28724

Immediate Actions Required

• Review and restrict file permissions on all NGINX Management Suite configuration files
• Audit user accounts with local access to systems running NGINX Management Suite
• Apply the latest security patches from F5 for affected products
• Implement principle of least privilege for all accounts accessing the management suite

Patch Information

F5 has released security updates to address this vulnerability. Organizations should consult the F5 Knowledge Article K000133233 for specific patch information and upgrade guidance. Additional advisory information is available from NetApp Security Advisory NTAP-20230609-0006.

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated and may remain vulnerable.

Workarounds

• Manually correct file permissions on sensitive NGINX Management Suite files to restrict access to administrative accounts only
• Implement additional access controls such as SELinux or AppArmor to enforce file access policies
• Limit local user access to systems running NGINX Management Suite components
• Deploy file integrity monitoring to detect unauthorized modifications until patches can be applied

# Example permission hardening for NGINX Management Suite
# Verify current permissions on sensitive directories
ls -la /etc/nms/
ls -la /var/lib/nms/

# Restrict permissions to root/admin only
chmod 600 /etc/nms/*.conf
chown root:root /etc/nms/*.conf

# Verify changes
stat /etc/nms/*.conf