CVE-2024-7634: F5 Nginx Agent Path Traversal Vulnerability

CVE-2024-7634 Overview

A path traversal vulnerability exists in F5 NGINX Agent's config_dirs restriction feature that allows a highly privileged attacker to write or overwrite files outside of the designated secure directory. This security bypass undermines the fundamental access controls designed to limit configuration file management to specific directories, potentially enabling attackers to compromise system integrity through arbitrary file manipulation.

Critical Impact

Highly privileged attackers can bypass directory restrictions to write or overwrite arbitrary files on the system, potentially leading to configuration tampering, privilege escalation, or system compromise.

Affected Products

• F5 NGINX Agent
• F5 NGINX Instance Manager

Discovery Timeline

• August 22, 2024 - CVE-2024-7634 published to NVD
• January 24, 2025 - Last updated in NVD database

Technical Details for CVE-2024-7634

Vulnerability Analysis

This vulnerability is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), commonly known as path traversal. The NGINX Agent implements a config_dirs feature intended to restrict file operations to designated secure directories. However, the implementation fails to properly validate and sanitize file paths, allowing attackers to use path traversal sequences to escape the restricted directory boundaries.

The vulnerability requires high privileges to exploit, meaning an attacker would need authenticated access with elevated permissions to the NGINX Agent management interface. Despite this requirement, successful exploitation enables writing or overwriting files outside the intended configuration directories, which could have significant security implications for the affected system.

Root Cause

The root cause of this vulnerability lies in insufficient path validation within the NGINX Agent's file handling routines. When the config_dirs restriction feature processes file paths, it fails to properly canonicalize and validate paths before performing write operations. This allows specially crafted paths containing directory traversal sequences (such as ../) to bypass the intended directory restrictions and access locations outside the secure configuration directories.

Attack Vector

The attack is network-accessible and requires no user interaction. An attacker with high-level privileges to the NGINX Agent must craft malicious requests that include path traversal sequences in file path parameters. When processed by the vulnerable config_dirs feature, these paths allow file write operations to escape the designated directories and target arbitrary locations on the filesystem.

The vulnerability enables file overwrite capabilities, which an attacker could leverage to:

• Modify critical system configuration files
• Plant malicious scripts or executables
• Overwrite logging configurations to hide malicious activity
• Potentially achieve further privilege escalation by modifying setuid binaries or cron configurations

Detection Methods for CVE-2024-7634

Indicators of Compromise

• Unexpected file modifications outside designated NGINX configuration directories
• Presence of path traversal sequences (../, ..\) in NGINX Agent logs or requests
• Unauthorized configuration changes to system files or directories
• Anomalous file write operations originating from NGINX Agent processes

Detection Strategies

• Monitor NGINX Agent logs for requests containing path traversal patterns such as ../ or encoded variants
• Implement file integrity monitoring (FIM) on critical system directories to detect unauthorized modifications
• Audit privileged user activities within NGINX Agent management interfaces
• Deploy network-based intrusion detection rules to identify path traversal attempts in NGINX Agent traffic

Monitoring Recommendations

• Enable comprehensive logging for all NGINX Agent file operations
• Set up alerts for file write operations that target directories outside config_dirs boundaries
• Monitor for unusual patterns in privileged user authentication to NGINX Agent
• Review access logs for repeated failed attempts that may indicate exploitation attempts

How to Mitigate CVE-2024-7634

Immediate Actions Required

• Apply the latest security patches from F5 for NGINX Agent and NGINX Instance Manager
• Review and restrict privileged access to NGINX Agent management interfaces
• Implement additional access controls and network segmentation to limit exposure
• Audit existing configurations for signs of compromise

Patch Information

F5 has released security updates to address this vulnerability. Administrators should consult the F5 Security Advisory K000140630 for detailed patching instructions and affected version information. Apply all available updates to NGINX Agent and NGINX Instance Manager deployments.

Workarounds

• Implement strict network access controls to limit which systems can reach NGINX Agent management interfaces
• Apply the principle of least privilege by reviewing and reducing the number of highly privileged accounts
• Use additional file system permissions to protect critical directories from modification
• Consider implementing web application firewall (WAF) rules to block path traversal patterns in requests to NGINX Agent

# Example: Restrict network access to NGINX Agent management port
# Add firewall rules to limit access to trusted management networks only
iptables -A INPUT -p tcp --dport 8081 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8081 -j DROP