Top 10 Open-Source Firewalls to Secure Your Network in 2026
In today’s digital landscape, safeguarding network infrastructure is paramount. Open-source firewalls have emerged as cost-effective, transparent, and customizable solutions for organizations seeking robust security measures. These firewalls monitor and control network traffic based on predefined rules, offering flexibility and community-driven support. Below, we explore the top 10 open-source firewalls in 2026, highlighting their features and recent developments.
1. pfSense
pfSense is a FreeBSD-based firewall and router platform renowned for its enterprise-grade features and user-friendly web interface. It offers functionalities such as VPN support, load balancing, and detailed reporting. However, users should be aware of vulnerabilities like CVE-2022-31814, which allowed remote code execution attacks, particularly affecting installations with the pfBlockerNG package. Regular updates and community support help mitigate such risks.
2. OPNsense
Celebrating its 10th anniversary, OPNsense released version 25.1, codenamed Ultimate Unicorn, built on FreeBSD 14.2. This update introduced enhanced security zone configurations, a redesigned user interface, and improved hardware compatibility. OPNsense’s commitment to security and user experience makes it a strong contender in the open-source firewall arena.
3. IPFire
IPFire 2.29 Core Update 198 brought significant enhancements, including an upgraded Intrusion Prevention System (IPS) powered by Suricata 8.0.1. The update introduced new reporting tools, allowing administrators to receive real-time email notifications for critical alerts and generate scheduled PDF reports. These features enhance network monitoring and threat response capabilities.
4. SafeLine
SafeLine is a free, next-generation web application firewall (WAF) developed by Chaitin Tech. It gained popularity in 2025, boasting 17.5k stars on GitHub and over 400,000 deployments worldwide. SafeLine integrates a zero-trust security model, offering identity authentication features like Single Sign-On (SSO) and two-factor authentication (2FA). Its semantic analysis engine reduces false positives and negatives, providing robust protection against emerging threats.
5. ModSecurity
ModSecurity is an open-source WAF engine widely used for its versatility. However, a vulnerability identified as CVE-2025-52891 exposed systems to denial-of-service attacks via empty XML tags. Administrators are advised to disable the SecParseXmlIntoArgs feature or apply the latest patches to mitigate this risk. Despite this, ModSecurity remains a powerful tool for web application protection.
6. SonicWall SonicOS
SonicWall’s SonicOS faced a critical vulnerability (CVE-2024-40766) that allowed unauthorized access and potential firewall crashes. The issue affected multiple generations of devices, emphasizing the importance of timely firmware updates and restricting management access to trusted sources. SonicWall’s swift response underscores its commitment to product security.
7. Kerio Control
Kerio Control, a popular firewall and Unified Threat Management (UTM) product, was found to have a critical vulnerability (CVE-2024-52875) enabling one-click remote code execution. The flaw affected versions 9.2.5 through 9.4.5. Users are urged to update to Version 9.4.5 Patch 2 to address this issue. Kerio Control offers features like VPN support, bandwidth management, and detailed reporting.
8. Sophos Firewall
Sophos addressed three critical vulnerabilities (CVE-2024-12727, CVE-2024-12728, and CVE-2024-12729) in its firewall product, which could allow remote code execution under specific conditions. Hotfixes have been released, and users are advised to apply them promptly. Sophos Firewall provides comprehensive security features, including intrusion prevention, VPN, and web filtering.
9. Meta’s Llama Firewall
Meta’s Llama Firewall faced bypasses due to prompt injection vulnerabilities, raising concerns about the effectiveness of existing large language model (LLM) security measures. The findings highlight the need for more robust defenses as enterprises increasingly integrate LLMs into their workflows. Continuous evaluation and improvement are essential for maintaining security in evolving technological landscapes.
10. Wallbleed Vulnerability in China’s Great Firewall
A study revealed a critical vulnerability in China’s Great Firewall DNS system, termed Wallbleed, which allowed sensitive memory data leaks for over two years before being patched in March 2024. This flaw exposed up to 125 bytes of memory per request from censorship middleboxes, posing severe privacy risks to global internet users. The incident underscores the importance of regular security assessments and prompt patching.
Conclusion
Open-source firewalls offer transparent, flexible, and cost-effective solutions for network security. However, staying vigilant about vulnerabilities and applying timely updates are crucial to maintaining robust protection. By leveraging the strengths of these top 10 open-source firewalls and adhering to best practices, organizations can effectively safeguard their network infrastructures in 2026 and beyond.
