SSTP vs. OpenVPN: What’s the Difference?

Last updated on March 19, 2025

The main difference between SSTP and OpenVPN is that SSTP is less secure than OpenVPN. This is because SSTP uses the deprecated SSL 3.0 protocol which is vulnerable to the POODLE bug. On the other hand, OpenVPN uses the TLS protocol which is generally more secure and is not affected by POODLE. Another difference between SSTP and OpenVPN is that SSTP primarily works on Windows and might be hard to configure on other operating systems, whereas OpenVPN works on every platform. Read on to learn more about the differences between SSTP vs. OpenVPN.

SSTP vs. OpenVPN: Key Differences and Best Use Cases

When evaluating VPN protocols, it’s essential to understand the distinctions between Secure Socket Tunneling Protocol (SSTP) and OpenVPN to determine which best fits your needs.​

Key Differences

• Security: OpenVPN leverages the OpenSSL library and SSLv3/TLSv1 protocols, offering robust security measures. In contrast, SSTP, developed by Microsoft, is considered secure but is less transparent due to its proprietary nature.
  Compatibility: OpenVPN is renowned for its cross-platform support, functioning seamlessly on various operating systems, including Windows, macOS, Linux, and mobile platforms. SSTP, however, is predominantly designed for Windows environments, limiting its compatibility with other operating systems.
  Performance: Both protocols offer reliable performance. OpenVPN’s flexibility allows it to be configured for either UDP or TCP ports, optimizing speed and reliability. SSTP operates over TCP port 443, which can be advantageous in networks with strict firewall rules but may result in slightly reduced performance compared to OpenVPN. 

Best Use Cases

• OpenVPN: Ideal for users seeking a balance between high security and cross-platform compatibility. Its open-source nature allows for extensive customization, making it suitable for diverse networking environments.​
  SSTP: Best suited for users within Windows-centric infrastructures or in scenarios where VPN traffic needs to blend with regular HTTPS traffic to bypass strict firewalls. Its integration with Windows platforms ensures seamless deployment in such environments.

What is SSTP?

SSTP stands for Secure Socket Tunneling Protocol, a VPN protocol developed by Microsoft that allows you to create a secure connection to a VPN server over the internet. It uses SSL/TLS encryption, the same technology that protects your web browsing, to encrypt and authenticate your VPN traffic. SSTP is mainly designed for Windows devices, but it can also work on Linux and macOS with some configuration.

How Does SSTP Work?

SSTP works by tunneling PPP (Point-to-Point Protocol) frames over an HTTPS connection. 

• PPP is a protocol that establishes a link between two devices and allows them to exchange data.
• HTTPS is a protocol that secures web traffic using SSL/TLS encryption.

By using HTTPS, SSTP can bypass most firewalls and censorship tools that may block other VPN protocols. SSTP uses TCP port 443, which is the same port used by HTTPS traffic, to establish and maintain the VPN connection.

What is OpenVPN?

OpenVPN is an open-source VPN protocol that offers a high level of security and performance. OpenVPN can use various encryption algorithms, such as AES-256, to protect your VPN traffic from hackers and spies. It can also use different transport protocols, such as UDP or TCP, to optimize your VPN speed and reliability. OpenVPN is compatible with almost all platforms, including Windows, Mac, Linux, Android, iOS, and more.

How Does OpenVPN Work?

OpenVPN works by creating a virtual tunnel between your device and a VPN server using TLS encryption.

• TLS is a protocol that secures web traffic using certificates and keys.

OpenVPN can use either pre-shared keys or certificates to authenticate the VPN server and the client. It can also use UDP or TCP as the underlying transport protocol. UDP is faster but less reliable, while TCP is slower but more reliable. OpenVPN can use any port number, but it usually uses UDP port 1194 or TCP port 443.

What is a POODLE Attack?

The POODLE (Padding Oracle on Downgraded Legacy Encryption) attack is a complex cyberattack whereby the attacker can eavesdrop on communication encrypted using SSL 3.0. The POODLE vulnerability is only present in the outdated Secure Sockets Layer (SSL) protocol. It is no longer present in the newer Transport Layer Security protocol (TLS). Since SSTP uses SSL and OpenVPN uses TLS, OpenVPN has a huge advantage over SSTP in terms of security. 

Note: The POODLE attack was originally designed to exploit a vulnerability in the SSL 3.0 protocol, which is no longer present in the TLS protocol. However, a variant of the POODLE attack was discovered that can also affect some implementations of TLS, if they do not validate the encryption padding properly. This means that some servers may still be vulnerable to POODLE, even if they disable SSL and use TLS instead.

What’s the Difference Between SSTP and OpenVPN?

Next to PPTP and L2TP/IPsec, SSTP and OpenVPN are the most popular VPN protocols. Since choosing the tunneling protocol is the key choice in VPNs, here is a table that outlines all the major differences between SSTP and OpenVPN.

SSTP	OpenVPN
Short for Secure Socket Tunneling Protocol.	Sometimes shortened to OVPN; VPN stands for Virtual Private Network.
Microsoft’s proprietary encryption standard	Open source
SSTP does not require you to install third-party software.	OpenVPN depends on third-party software.
SSTP uses TCP.	OpenVPN can use UDP or TCP.
Limited configuration capabilities.	Highly configurable and customizable.
SSTP uses AES-256 encryption.	OpenVPN can use strong SSL encryption such as Blowfish-128 AES-256 encryption.
Uses deprecated SSL 3.0, which is a big security concern (vulnerable to POODLE attacks).	Uses TLS which is not impacted by most variants of POODLE cyberattacks.
SSTP fully integrates with Windows. While SSTP also supports Linux and macOS, it may be very hard to configure SSTP on a non-Windows device.	OpenVPN is available on Windows XP and later as well as Solaris, macOS, Linux, iOS, Android, and many other desktop and mobile operating systems.
Easy to set up.	Might be difficult to configure.

Advantages of OpenVPN over SSTP

• OpenVPN uses TLS instead of SSL, which makes it not susceptible to POODLE attacks.
• OpenVPN can run over UDP, which makes it faster.
• OpenVPN is highly customizable, which allows more flexibility and the use of very secure encryption algorithms such as AES-256.
• OpenVPN is open source, which means it is regularly inspected, maintained, and updated by its community of supporters.
• OpenVPN works on every platform, whereas SSTP may have compatibility issues with non-Windows devices.

Advantages of SSTP over OpenVPN

• SSTP is more stable and easier to set up on Windows devices, as it is a proprietary protocol developed by Microsoft.
• SSTP uses TCP port 443 by default, which is the same port used by HTTPS traffic. This makes it harder to detect and block by firewalls and censorship tools.

SSTP vs. OpenVPN: Vulnerabilities to Cyberattacks

Understanding the potential vulnerabilities of SSTP and OpenVPN is crucial for implementing effective security measures.​

SSTP Vulnerabilities

• Proprietary Limitations: As a Microsoft-developed protocol, SSTP’s closed-source nature limits external security evaluations, potentially obscuring undiscovered vulnerabilities. ​
• POODLE Attack: SSTP uses SSL, so it is vulnerable to the POODLE attack.

OpenVPN Vulnerabilities

• Configuration Complexity: OpenVPN’s extensive configurability can lead to misconfigurations if not managed properly, potentially exposing security weaknesses. ​

Mitigation Strategies

• Multi-Factor Authentication: Enable company-wide MFA for all your employees to safeguard your infrastructure against the most common attacks on passwords.
• Regular Updates: Keep VPN software up to date to patch known vulnerabilities promptly.​
• Secure Configurations: Adhere to best practices for VPN configurations to minimize security risks.

Exploring Other VPN Protocols: WireGuard and IKEv2

Beyond SSTP and OpenVPN, other VPN protocols like WireGuard and IKEv2 offer unique features that may align better with specific user requirements.​

WireGuard

• Simplicity: With a smaller codebase, WireGuard is easier to audit and maintain, potentially reducing security vulnerabilities.
• Performance: Known for its high-speed performance and efficiency, WireGuard is designed to be faster and leaner than traditional VPN protocols.

OpenVPN vs. WireGuard: What’s the Difference? →

IKEv2

• Stability: IKEv2 is recognized for its ability to maintain a stable VPN connection, especially during network changes, making it ideal for mobile users. ​
• Security: It offers robust security features and is widely supported across various platforms.

IKEv2 vs. OpenVPN: What’s the Difference? →

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Conclusion of SSTP vs. OpenVPN: Which One Should You Use?

SSTP is a fast and stable VPN protocol that works well on Windows devices, but it has some security drawbacks due to its use of SSL 3.0. In contrast, OpenVPN is a more secure and versatile VPN protocol that works on every platform and offers more configuration options. Use OpenVPN if you can.