CVE-2024-41637: RaspAP Privilege Escalation Vulnerability

CVE-2024-41637 Overview

CVE-2024-41637 is a privilege escalation vulnerability affecting RaspAP versions prior to 3.1.5. The vulnerability exists because the www-data user has write access to the restapi.service file and also possesses sudo privileges to execute several critical commands without requiring a password. This combination of excessive permissions allows an attacker with low-privileged access to escalate their privileges on the affected system.

Critical Impact

An attacker can leverage misconfigured file permissions and passwordless sudo access to achieve privilege escalation on RaspAP installations, potentially gaining full root access to the underlying Raspberry Pi system.

Affected Products

• RaspAP versions prior to 3.1.5
• RaspAP WebGUI installations with default configurations
• Raspberry Pi systems running vulnerable RaspAP deployments

Discovery Timeline

• 2024-07-29 - CVE-2024-41637 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-41637

Vulnerability Analysis

This vulnerability is classified as CWE-77 (Improper Neutralization of Special Elements used in a Command), manifesting as a privilege escalation issue. The root problem lies in RaspAP's permission model, which grants the web server user (www-data) excessive access to system-critical files and sudo capabilities.

The attack requires network access and low-level privileges (authenticated access to the RaspAP interface), but once these preconditions are met, exploitation is straightforward. The impact is significant, as an attacker can achieve high confidentiality and integrity compromise, with some availability impact on the target system.

For detailed technical analysis of this vulnerability, refer to the 0xZon Blog CVE-2024-41637 Analysis.

Root Cause

The vulnerability stems from insecure default permissions in RaspAP's deployment configuration. Specifically, the www-data user is granted:

1. Write access to restapi.service: This systemd service file can be modified by the web server user, allowing injection of arbitrary commands that execute with elevated privileges when the service is restarted.

2. Passwordless sudo privileges: The www-data user can execute several critical system commands via sudo without password authentication, providing a direct path to privilege escalation.

This combination creates a privilege escalation chain where a low-privileged attacker can modify service files and leverage sudo access to execute malicious commands as root.

Attack Vector

The attack vector is network-based, requiring an authenticated attacker with access to the RaspAP web interface. The exploitation flow involves:

1. Gaining initial access to the RaspAP system as the www-data user (via web application compromise or legitimate low-privileged access)
2. Modifying the restapi.service file to include malicious commands
3. Triggering service restart using available sudo privileges
4. Achieving code execution with elevated (root) privileges

The attack complexity is low, requiring no user interaction beyond the initial authenticated access. The vulnerability allows attackers to pivot from web application access to full system compromise on the underlying Raspberry Pi hardware.

Detection Methods for CVE-2024-41637

Indicators of Compromise

• Unexpected modifications to the /etc/systemd/system/restapi.service file or similar service configuration files
• Unusual sudo command execution by the www-data user in system logs
• New or modified cron jobs, scheduled tasks, or persistence mechanisms associated with the web server user
• Suspicious processes spawned as children of RaspAP-related services

Detection Strategies

• Monitor file integrity of systemd service files, particularly restapi.service, using file integrity monitoring (FIM) solutions
• Audit sudo usage by the www-data user and alert on execution of privileged commands
• Review /var/log/auth.log and /var/log/syslog for evidence of privilege escalation attempts
• Implement endpoint detection and response (EDR) to identify anomalous process execution chains

Monitoring Recommendations

• Enable auditd rules to track modifications to systemd service files in /etc/systemd/system/
• Configure centralized logging for all sudo command executions on RaspAP systems
• Deploy SentinelOne agents on Raspberry Pi systems running RaspAP to detect and respond to privilege escalation attempts in real-time
• Establish baseline behavior for the www-data user and alert on deviations

How to Mitigate CVE-2024-41637

Immediate Actions Required

• Upgrade RaspAP to version 3.1.5 or later immediately to address this vulnerability
• Audit current file permissions on the restapi.service file and restrict write access from the www-data user
• Review and minimize sudo privileges granted to the www-data user, removing unnecessary passwordless sudo access
• Isolate RaspAP systems from critical network segments until patching is complete

Patch Information

The vulnerability has been addressed in RaspAP version 3.1.5. Organizations should update their RaspAP installations to this version or later to remediate the privilege escalation vulnerability. The update can be obtained from the official GitHub RaspAP WebGUI Repository.

Workarounds

• Restrict file permissions on restapi.service to prevent write access by the www-data user: chmod 644 /etc/systemd/system/restapi.service and ensure root ownership
• Review and remove unnecessary sudo privileges from the www-data user in /etc/sudoers or sudoers.d configuration files
• Implement network segmentation to limit access to RaspAP management interfaces
• Enable mandatory access control (MAC) solutions like AppArmor or SELinux to restrict www-data user capabilities

# Restrict restapi.service file permissions
sudo chown root:root /etc/systemd/system/restapi.service
sudo chmod 644 /etc/systemd/system/restapi.service

# Review current sudo privileges for www-data
sudo grep -r "www-data" /etc/sudoers /etc/sudoers.d/

# Reload systemd after permission changes
sudo systemctl daemon-reload