Raspberry Pi Security Alert: Critical Vulnerabilities in Pi-hole, CrowdSec & Authelia

Introduction

The Raspberry Pi has revolutionized home network security, enabling enthusiasts and professionals alike to deploy enterprise-grade defensive stacks at minimal cost. The combination of Pi-hole (DNS-level ad blocking and tracking prevention), CrowdSec (collaborative threat intelligence and intrusion prevention), and Authelia (authentication gateway with two-factor authentication) represents a powerful trifecta for home network protection. However, recent security disclosures in April 2026 have exposed critical vulnerabilities affecting this seemingly robust architecture, requiring immediate attention from the millions of users relying on these systems.

According to Ubuntu Security Notice USN-8204-1, CVE-2024-36347 affects Linux kernel implementations on Raspberry Pi Real-time systems, while Pi-hole's April 2026 release addresses multiple web interface vulnerabilities. Simultaneously, Raspberry Pi OS 6.2 has disabled passwordless sudo functionality, marking a significant shift in the platform's security posture.

With over 30 million Raspberry Pi devices deployed worldwide and Pi-hole alone protecting millions of networks, these vulnerabilities represent a significant attack surface. As home networks increasingly host sensitive IoT devices, remote work infrastructure, and personal data repositories, understanding and mitigating these risks has never been more critical.

Understanding the Vulnerability Landscape

CVE-2024-36347: The Kernel-Level Threat

CVE-2024-36347 represents a medium-severity vulnerability with a CVSS score of 6.4, affecting AMD CPU microcode verification processes. According to the National Vulnerability Database, this flaw stems from improper signature verification in the AMD CPU ROM microcode patch loader. While originally an AMD processor issue, its inclusion in USN-8204-1 indicates that Ubuntu's Linux kernel for Raspberry Pi Real-time systems incorporates affected code paths.

The vulnerability allows an attacker with local administrator privileges to load malicious CPU microcode, potentially resulting in:

• Loss of integrity in x86 instruction execution
• Compromise of data confidentiality and integrity within CPU privileged contexts
• Potential exploitation of System Management Mode (SMM) execution environments
• Undermining of kernel-level security mechanisms that defensive stacks rely upon

Critical Note: While this vulnerability requires local administrator access, the historical passwordless sudo configuration in Raspberry Pi OS versions prior to 6.2 significantly lowered the barrier for privilege escalation attacks.

The Passwordless Sudo Vulnerability

For years, Raspberry Pi OS shipped with a convenience feature that would prove to be a significant security liability: passwordless sudo access. As detailed in the official Raspberry Pi security announcement, this configuration allowed any process running with the default 'pi' user credentials to execute administrative commands without authentication.

The security implications for defensive network stacks are severe. An attacker who gains initial access through any vector—whether through a compromised web service, social engineering, or exploitation of another vulnerability—could immediately escalate to root privileges. This would grant complete control over:

• Pi-hole's DNS resolution and filtering rules
• CrowdSec's threat intelligence data and blocking decisions
• Authelia's authentication policies and user credentials
• Docker container configurations and network isolation

Raspberry Pi OS 6.2, released in April 2026, addresses this issue by disabling passwordless sudo on new installations. However, existing systems remain vulnerable unless manually reconfigured.

Pi-hole Web Interface Vulnerabilities

The Pi-hole April 2026 security release addresses multiple critical vulnerabilities responsibly disclosed by security researcher andrejtomci. These include:

• Cross-Site Scripting (XSS) vulnerabilities in queries.js, the Network page, and Dashboard components
• HTML injection attacks targeting various web interface elements
• Local privilege escalation through the /etc/pihole/versions file being sourced by root-run scripts
• Missing CSRF token protection allowing state-changing operations without proper authentication

These vulnerabilities are particularly dangerous in defensive network stack deployments because Pi-hole typically operates as a trusted service. An attacker exploiting XSS vulnerabilities could:

1. Steal administrative session cookies to gain full Pi-hole control
2. Modify DNS filtering rules to redirect traffic to malicious servers
3. Disable blocking entirely, exposing the network to threats
4. Exfiltrate DNS query logs containing sensitive browsing information

Impact Analysis for Defensive Network Stacks

Attack Surface Mapping

A typical Raspberry Pi 4 defensive stack presents multiple attack vectors that these vulnerabilities expose:

Network Layer: Pi-hole operates as the network's DNS resolver, processing every domain lookup request. Compromising Pi-hole through web interface vulnerabilities grants attackers visibility into all network activity and the ability to manipulate DNS responses.

Application Layer: CrowdSec monitors logs and network traffic to identify malicious behavior. If the underlying kernel is compromised via CVE-2024-36347, attackers can manipulate or hide their activities from CrowdSec's detection mechanisms.

Authentication Layer: Authelia serves as the authentication gateway for protected services. With passwordless sudo access or kernel-level compromise, attackers can bypass Authelia entirely or extract credentials from memory and configuration files.

Cascading Failure Scenarios

The real danger lies in how these vulnerabilities can be chained together:

Scenario 1: Web-to-Root Compromise

1. Attacker exploits Pi-hole XSS vulnerability to gain administrative web access
2. Uses Pi-hole's teleporter backup feature to upload malicious configuration
3. Leverages passwordless sudo (on unpatched systems) to execute arbitrary commands as root
4. Loads malicious microcode via CVE-2024-36347 for persistent kernel-level access

Scenario 2: Lateral Movement

1. Initial compromise through any network service running on the Raspberry Pi
2. Privilege escalation via passwordless sudo or Pi-hole privilege escalation vulnerability
3. Modification of CrowdSec parsers and scenarios to hide malicious activity
4. Compromise of Authelia's database to access credentials for other network services

Real-World Risk Assessment

According to security stack deployment guides, most users run these services in Docker containers. While containerization provides some isolation, it's not a complete defense:

• Docker containers share the host kernel, making kernel vulnerabilities like CVE-2024-36347 particularly dangerous
• Privileged containers or those with host network access can directly interact with vulnerable system components
• Volume mounts between host and containers can be exploited for privilege escalation
• Default Docker configurations often prioritize convenience over security

Severity Assessment: While CVE-2024-36347 carries a CVSS score of 6.4 (Medium), its impact in the context of defensive network stacks is significantly higher due to the privileged nature of these services and the cascading effects of compromise.

Detection and Verification Methods

Identifying Vulnerable Systems

Before applying patches, you must determine your exposure. Follow these steps to assess your defensive network stack:

Step 1: Check Operating System Version

# For Raspberry Pi OS
cat /etc/os-release | grep VERSION

# For Ubuntu on Raspberry Pi
lsb_release -a

# Check kernel version
uname -r

# Verify if running Real-time kernel
uname -r | grep -i rt

Systems running Raspberry Pi OS versions prior to 6.2 or Ubuntu 24.04 LTS with Real-time kernel patches before the USN-8204-1 update are vulnerable.

Step 2: Verify Pi-hole Component Versions

# Check all Pi-hole component versions
pihole -v

# Expected safe versions:
# Pi-hole Core: v6.4.1 or higher
# Web Interface: v6.5 or higher
# FTL: v6.6 or higher

If any component shows a version lower than these thresholds, your Pi-hole installation contains known vulnerabilities.

Step 3: Test Passwordless Sudo Configuration

# Check sudo configuration for passwordless access
sudo grep -r "NOPASSWD" /etc/sudoers /etc/sudoers.d/

# Test if sudo requires password
sudo -k  # Clear cached credentials
sudo whoami  # Should prompt for password on secure systems

If sudo executes without requesting a password, your system has the passwordless sudo vulnerability.

Log Analysis for Compromise Indicators

Check for signs of exploitation in your system logs:

# Check for suspicious sudo usage
grep -i "sudo" /var/log/auth.log | grep -v "session opened"

# Examine Pi-hole query logs for unusual patterns
tail -n 1000 /var/log/pihole.log | grep -E "(\.\.|%|<|>|script)"

# Review CrowdSec decisions for blocked attacks
sudo cscli decisions list

# Check Docker container logs for anomalies
docker logs pihole 2>&1 | grep -i "error\|warning\|unauthorized"

Mitigation and Remediation Strategy

Immediate Actions (Critical Priority)

1. Update All Affected Components

For Raspberry Pi OS systems:

# Update system packages
sudo apt update
sudo apt full-upgrade -y

# Specifically update kernel packages
sudo apt install --only-upgrade raspberrypi-kernel

# Reboot to apply kernel updates
sudo reboot

For Ubuntu 24.04 LTS with Real-time kernel:

# Apply USN-8204-1 security update
sudo apt update
sudo apt install --only-upgrade linux-raspi-realtime

# Verify updated kernel version
sudo apt-cache policy linux-raspi-realtime

# Reboot to load patched kernel
sudo reboot

2. Update Pi-hole to Latest Versions

# Update Pi-hole components
pihole -up

# Verify updated versions
pihole -v

# Restart Pi-hole services
pihole restartdns

According to the official Pi-hole release notes, version 6.6 FTL, 6.5 Web, and 6.4.1 Core address all disclosed vulnerabilities.

3. Disable Passwordless Sudo

# Edit sudoers configuration
sudo visudo /etc/sudoers.d/010_pi-nopasswd

# Change this line:
# pi ALL=(ALL) NOPASSWD: ALL

# To this:
# pi ALL=(ALL) PASSWD: ALL

# Or remove the file entirely for maximum security
sudo rm /etc/sudoers.d/010_pi-nopasswd

Docker Security Hardening

For users running their defensive stack in Docker containers, implement these additional protections:

# Example docker-compose.yml hardening for Pi-hole
version: '3'
services:
  pihole:
    image: pihole/pihole:latest
    security_opt:
      - no-new-privileges:true
    cap_drop:
      - ALL
    cap_add:
      - NET_ADMIN
      - NET_BIND_SERVICE
      - CHOWN
      - DAC_OVERRIDE
    read_only: true
    tmpfs:
      - /tmp
      - /var/run
    volumes:
      - './etc-pihole:/etc/pihole:rw'
      - './etc-dnsmasq.d:/etc/dnsmasq.d:rw'
    environment:
      - WEBPASSWORD=your_secure_password_here
    restart: unless-stopped

Key security improvements:

• no-new-privileges prevents privilege escalation within containers
• cap_drop: ALL followed by selective cap_add implements least-privilege principle
• read_only: true prevents container filesystem modifications
• tmpfs mounts for temporary data that must be writable

CrowdSec and Authelia Configuration Updates

Ensure your entire defensive stack benefits from the security updates:

# Update CrowdSec
sudo cscli hub update
sudo cscli hub upgrade

# Update all CrowdSec collections and parsers
sudo cscli collections upgrade --all
sudo cscli parsers upgrade --all

# Restart CrowdSec service
sudo systemctl restart crowdsec

# For Docker-based Authelia, pull latest image
docker pull authelia/authelia:latest
docker-compose up -d authelia

Long-Term Security Posture Improvements

Implementing Defense in Depth

The April 2026 vulnerabilities highlight the importance of layered security. A comprehensive defensive network stack should include:

1. Network Segmentation

• Isolate your Raspberry Pi defensive stack on a dedicated VLAN
• Implement firewall rules restricting access to administrative interfaces
• Use CrowdSec's firewall bouncer to automatically block detected threats

2. Access Control Hardening

• Enable two-factor authentication in Authelia for all protected services
• Configure Authelia to protect Pi-hole's web interface
• Use SSH key-based authentication instead of passwords
• Disable root SSH login entirely

3. Monitoring and Alerting

# Configure CrowdSec to send alerts
sudo cscli notifications add email_alerts \
  --type email \
  --to [email protected]

# Set up Pi-hole query logging with retention limits
pihole -l on

# Configure system audit logging
sudo apt install auditd
sudo systemctl enable auditd
sudo systemctl start auditd

Automated Update Management

Prevent future vulnerabilities through automated patching:

# Install unattended-upgrades
sudo apt install unattended-upgrades apt-listchanges

# Configure automatic security updates
sudo dpkg-reconfigure -plow unattended-upgrades

# Create Pi-hole update cron job
echo "0 3 * * 0 pihole -up" | sudo tee /etc/cron.d/pihole-update

Best Practice: While automated updates improve security, always maintain recent backups of your configuration. Pi-hole's teleporter feature and Docker volume backups ensure you can recover from update-related issues.

Regular Security Auditing

Implement a monthly security review process:

1. Review CrowdSec's detected and blocked threats: sudo cscli metrics
2. Analyze Pi-hole's query logs for suspicious domains or patterns
3. Check Authelia's authentication logs for failed login attempts
4. Verify all components are running latest stable versions
5. Review Docker container security with tools like Docker Bench for Security

Conclusion

The convergence of CVE-2024-36347, Pi-hole web interface vulnerabilities, and Raspberry Pi OS's passwordless sudo configuration represents a critical security moment for defensive network stack deployments. While each vulnerability individually poses moderate risk, their combination creates a dangerous attack surface that could compromise entire home networks.

The good news is that comprehensive patches are available across all affected components. By following the mitigation steps outlined in this article—updating to Raspberry Pi OS 6.2, upgrading to Pi-hole 6.6/6.5/6.4.1, applying USN-8204-1, and implementing defense-in-depth strategies—you can restore and enhance your network's security posture.

The April 2026 security releases also mark a positive shift in the Raspberry Pi ecosystem's security maturity. The removal of passwordless sudo, responsible disclosure of Pi-hole vulnerabilities, and rapid patch deployment demonstrate a growing commitment to security that benefits millions of users worldwide.

Remember that security is not a one-time configuration but an ongoing process. Regular updates, monitoring, and security audits ensure your defensive network stack continues protecting your network against evolving threats. The combination of Pi-hole, CrowdSec, and Authelia remains one of the most powerful home network security solutions available—when properly maintained and secured.