A VPN is the most effective way for consumers to gain online privacy. Reliable VPNs encrypt your internet traffic, hide your IP address from the websites you visit, and prevent local networks and ISPs from tracking your online activities. The caveat? Not all consumer-facing VPNs offer the same level of protection. Keep reading to learn about common VPN vulnerabilities.
VPN apps, protocols, servers, and privacy policies can all contain weaknesses. A poorly designed VPN could leak your IP address or DNS requests, meaning it wouldn’t actually stop third parties from monitoring your traffic. Other VPNs fail to protect you when the connection drops, or have been found to collect information about subscribers’ activities.
In this guide, I explain the most common vulnerabilities that affect consumer VPNs, including IP, DNS, and WebRTC leaks, kill-switch failures, weak encryption protocols, and logging risks.
What is a VPN Vulnerability?
A VPN isn’t designed to protect you from the VPN provider. It is designed to give you privacy from everyone else. This makes what the VPN provider does with data extremely important.
The best VPNs promise to route your traffic through shared servers, where it’s mixed with that of dozens, if not hundreds, of other users. This shared-server environment supports privacy by design because it is harder to track what any individual user is doing. Top VPNs also use completely diskless servers that run in RAM. This prevents sensitive user data from being stored persistently on a hard drive. If the VPN provider pulls the plug on a server, the data in volatile memory disappears.
The final puzzle piece that makes a VPN trustworthy is a no-logging policy. This is a privacy commitment in which the VPN promises not to keep identifying logs such as your source IP address, connection timestamps, the server you used, or the websites you visit.
With those logs never retained, the VPN has no historical record of what you did while connected, which means it cannot hand over activity logs if authorities serve it with a legally binding data request.
The six common types of VPN vulnerabilities
A VPN vulnerability is anything that brings the efficacy, trustworthiness, or security of these protections into question.
It could be a flaw in the VPN app’s design that lets attackers exploit VPN sessions. It could be a poorly written privacy policy, or a deliberately invasive one that creates gray areas, loopholes, or even allows outright data collection.
Generally speaking, VPN vulnerabilities fall into six categories, and in this guide I will walk you through each of them:
- Software and app exploits
- Protocol weaknesses
- DNS and IP leaks
- Logging and data exposure
- Server infrastructure vulnerabilities
- Authentication flaws
Software and app exploits
Consumer VPN apps need deep access to your operating system to create network interfaces, change routing and DNS settings, enforce a kill switch, and run other privacy features. Some security features integrate even further. On my own Windows PC, for example, I found that NordVPN’s Threat Protection had installed a trusted root certificate.
This isn’t inherently a security problem, and it isn’t a reason to consider a VPN as spyware or untrustworthy. However, it’s an important reminder of the level of system access and authority VPN software can have over your operating system.
If an attacker discovered a significant zero-day vulnerability in a VPN client, the permissions needed to make the VPN work could potentially allow vertical privilege escalation. Depending on what access the compromised device has, the attacker could then use it as a foothold for lateral movement into other parts of a network.
VPN app vulnerabilities and privilege escalation
NordVPN is a useful real-world example. In 2018, Cisco Talos researcher Paul Rascagneres discovered CVE-2018-3952 in NordVPN for Windows 6.14.28.0. The flaw could have let malware from a previous infection exploit the VPN to gain deeper access to the system, specifically by bypassing NordVPN’s configuration filters and executing commands with SYSTEM privileges.
The weakness stemmed from how NordVPN’s background Windows service validated OpenVPN configuration files.
Nord developers designed this background service to block configurations that could launch other programs. However, this protection failed if a hacker placed the instructions inside quotation marks. Because NordVPN has SYSTEM privileges, successfully exploiting the flaw could give hackers the same access and control as the Windows operating system itself.
How NordVPN responded to the flaw
The good news is that Cisco Talos did not report any evidence that the vulnerability had already been exploited in the wild when it disclosed the flaw to NordVPN. That said, as with any zero-day vulnerability, it is impossible to know whether another attacker found and used it before the problem was fixed. No evidence does not mean no possible attacks.
We do know, though, that Cisco Talos privately disclosed the flaw to NordVPN on July 5, 2018. And Nord released a fix on August 8, which is a reasonably fast response.
This case strongly shows why app-level VPN vulnerabilities and rapid patch management matter. Complex VPN software can contain bugs just like any other application. The difference is that VPN clients often require system-level privileges that can make exploitation more dangerous.
An important clarification: auditing for vulnerabilities and patching them when they are found is a natural part of software development. This NordVPN case should not be taken as evidence of wrongdoing or lax software development. Unfortunately, bugs are found, and a company’s response to those flaws matters most.
Protocol weaknesses
Encryption protocols are the part of the VPN that allow it to create and maintain a secure tunnel to the VPN server. If the protocol is outdated, badly implemented, or configured incorrectly, it weakens or potentially even destroys the privacy that the VPN is supposed to give you.
PPTP, for example, is an outdated protocol that has been deprecated due to significant cryptographic weaknesses. It should no longer be considered secure for maintaining online privacy, though it can be used for location spoofing when no privacy is needed. L2TP/IPsec is much safer than PPTP, but it is nearing end of life and relies heavily on implementation accuracy to maintain user privacy.
OpenVPN is much harder to attack, but it relies heavily on configuration choices, meaning OpenVPN can be secure or insecure depending on how a VPN implements it. Poor certificate validation, for example, can expose users to a man-in-the-middle attack, while weak cipher choices or badly configured authentication settings can undermine the security of an otherwise reliable protocol.
This is why I always analyze OpenVPN config files manually during VPN reviews to check the handshake, authentication, cipher strength, and whether Perfect Forward Secrecy is implemented. Having OpenVPN as an option in the app doesn’t tell the full story when reviewing VPNs.
When choosing a VPN provider, I recommend sticking to services that prioritize modern protocols and forward-thinking improvements such as quantum preparedness, rather than providers that keep outdated options like PPTP available just to make the app look more capable than it really is. WireGuard is the best choice.
DNS, IP, and WebRTC leaks
DNS leaks happen when the VPN client fails to encapsulate DNS requests within the encrypted tunnel. This can let your ISP or local Wi-Fi network see which domains you are trying to access, even when the VPN is connected and appears to be working properly.
IP leaks happen when your real IPv4 or IPv6 address is exposed despite the VPN connection. This usually happens because of routing problems, lack of IPv6 support, or other flaws in how the VPN handles traffic. These leaks let websites see your home IP address, which can link your activity back to you and give you a false sense of security.
WebRTC leaks happen when browser-based WebRTC requests expose IP information that the VPN is designed to hide. This creates a kind of loophole that destroys the VPN’s privacy at the browser level.
These problems don’t require a hacker to launch sophisticated attacks. They simply happen silently in the background, breaking the VPN’s ability to provide the privacy it promised. Leaks like this happen because of a badly configured VPN app, a broken server, incorrect routing, or poorly implemented DNS leak protection.
What VPN leak testing reveals and why it affects VPN rankings
I have encountered these types of leaks many, many times while reviewing VPNs over the years, which is why I test for DNS, IPv4, IPv6, and WebRTC leaks on multiple servers rather than assuming that one successful connection proves everything is working properly. Usually, the offending VPN works perfectly on most servers but leaks DNS or IP on a single server.
I’ve also discovered servers advertised in one location that actually resolve to another, and virtual locations that accidentally reveal where the physical server is really based. As with leaks, these issues usually stem from configuration or implementation problems on the VPN provider’s side, which is why I always deduct points and point the finger.
You can learn how to carry out IP, DNS, and WebRTC leak tests yourself on any VPN service by following the link.
Logging and data exposure
A VPN can have well-designed apps, modern protocols with strong encryption, and reliable leak protection, and yet still let you down. That is why some popular technology influencers complain about VPNs and even mistakenly claim they don’t protect your privacy. These claims are ridiculous because they fail to comprehend who a VPN protects your privacy from.
The one thing we can all agree on is that VPN use relies on trust. And if you don’t trust the VPN provider you choose, that is the single strongest reason to switch to another service.
A VPN explains how it will treat your data internally in its privacy policy. If that policy admits to recording enough information about what its subscribers are doing, or storing connection logs that could later link you to your activities, the VPN has failed at the most important part of the trust relationship. The same applies if the policy contains gray areas that create enough confusion to potentially allow logging and data-use practices that put users at risk.
Why VPN logging policies matter
A VPN’s logging policy explains what information the provider collects, stores, and retains about its subscribers. The best VPNs use a no-logs policy. This means they don’t keep any information that can be used to link individual users to their online activities.
This includes not collecting or storing connection timestamps, source IP addresses, server choices, session identifiers, usage logs, or any metadata that could be used to link a subscriber to their VPN activity.
When a VPN stores user data, it turns that information into a target, even if the provider never intended to use it nefariously itself. It means the VPN can be forced to provide information about its users’ activities in response to government warrants or other legal requests, including subpoenas and DMCA-related demands. It also opens the door to unnecessary risks such as data leaks, data theft, breaches, and even internal access by rogue employees.
Server infrastructure vulnerabilities
Beyond modern protocols, the VPN must run a watertight server infrastructure configured and maintained to the same high standard across its entire network. This is harder than it sounds when a VPN has hundreds or even thousands of servers spread across data centers worldwide.
If an attacker gains access to a VPN server, they could potentially monitor connection metadata for everybody using that server, including destination IPs, timing, traffic volumes, and information that may reveal which domains users are accessing. This makes a server-side attack one of the biggest risks a VPN provider must mitigate.
Third-party VPN servers and infrastructure risks
Many VPNs rent at least some of their servers from third-party data centers. This creates another layer of risk because the VPN provider does not necessarily control every part of the underlying hardware or management environment. A server can appear correctly configured by the VPN provider while still having an insecure remote-management interface, unnecessary access account, or other weakness introduced at the data-center level.
Authentication flaws
As with all other accounts and services, weak authentication and account security can be a leading cause of compromise. The good news is that even if a hacker gains access to your account, they can’t break the encrypted tunnel to see what you are doing online.
Authentication vulnerabilities could allow hackers to log in, change settings, access account information, see which servers you connected to last (if they appear in recently used or favorites), and potentially use your VPN subscription to engage in nefarious activities.
If authorities investigate those activities while they are still ongoing, they could use targeted monitoring and traffic correlation to link the activity to your account. This could make you a prime suspect in the investigation.
It is worth noting that being linked to the activity through your VPN account would not necessarily mean the investigation ends with you. Investigators could also examine the source IP that was actually connecting to the VPN. If that points to a different location, and you can prove you were somewhere else when the activity took place, this would provide strong evidence that someone else compromised and used your account.
How VPN accounts are compromised
The primary methods of account compromise include phishing, brute forcing, or credential stuffing. In the latter, attackers take usernames and passwords exposed in previous data breaches and try them when logging in to the VPN. This is why it is crucial to use a unique password and to set up multi-factor authentication (MFA) for your VPN account.
Besides the end user’s responsibility to set up a strong password, the VPN must have security in place for password resets, account recovery, and session tokens. If any of these processes are weak or implemented incorrectly, hackers could take over a VPN account.
VPN providers should remember that a VPN can provide a highly secure tunnel using well-known encryption standards such as AES-256 or ChaCha20. However, this doesn’t matter if your account lacks strong security.
What separates a secure VPN from a vulnerable one?
A secure VPN is a reputable service based in a jurisdiction that allows it to operate comfortably with a no-logging policy that promises never to retain any records of your activities, your source IP address, or the servers you connect to.
The apps should be designed to provide robust protection against tunnel compromise, with trusted, future-proof encryption options and properly implemented ciphers, with the implementation independently audited. In addition to modern protocols, the VPN must run highly secure infrastructure with protection against multiple points of failure.
Conclusion
The best VPNs understand that user privacy relies not on one single feature, but on a stack of privacy-enhancing technologies working together. This includes modern protocols with properly implemented encryption, reliable leak protection, a kill switch that prevents your data from escaping if the VPN connection drops, diskless servers, obfuscation to make VPN traffic appear like regular internet traffic, and potentially extras such as server-side tracker and malware blocking.
Our VPN testing and ranking methodology accounts for all of these factors, so no matter which VPN list, review, or article you read, you will know services were chosen because they meet the latest security standards and fit your use case.
The caveat? No VPN can guarantee that a previously unknown zero-day vulnerability will never be discovered. New weaknesses can emerge in almost any piece of software, including VPNs. That is why a VPN provider’s track record matters. It is not necessarily historical vulnerabilities that matter most, but how the VPN provider handled them and whether, despite those discoveries, the VPN maintained a clean sheet when it came to protecting users’ privacy.
I also favor VPNs with active roadmaps and development teams. This shows a concerted effort to keep improving the service. A VPN that keeps developing is much easier to trust than one that appears to be standing still.
Frequently asked questions
Can any VPN be completely secure?
No. New vulnerabilities can always be discovered, which is why a provider’s track record, fast patching, and independent audits matter.
What should I do if my VPN reports a security vulnerability?
Read the provider’s advisory to understand what was affected. If your app is vulnerable, refrain from using it until a patch is available, then update the VPN immediately.
What happens if a VPN encryption key is stolen?
If an attacker obtains an encryption key, they could potentially decrypt traffic protected by that key. This is why reputable VPNs use Perfect Forward Secrecy (PFS), which regularly creates fresh session keys. If one key is compromised, it should not allow an attacker to go back and decrypt previous VPN sessions.
Can VPN encryption become vulnerable over time?
Yes. Encryption that was once considered secure can become weaker as new attacks are discovered and computing power improves. Outdated ciphers, hash functions, or key-exchange methods can eventually become unsafe, which is why reputable VPNs retire older cryptography and update their protocols as security standards evolve.
Do enterprise VPNs have different vulnerabilities?
This article focuses specifically on consumer-facing VPN services. Enterprise remote-access, site-to-site, and intranet VPNs can suffer from a different set of vulnerabilities involving VPN gateways, access controls, internal network architecture, and enterprise appliances, which fall outside the scope of this consumer-facing guide.
