IPSec vulnerabilities and fixes – A quick look

IPSec vulnerabilities and fixes – A quick look

Table of Contents

Any vulnerability can weaken your systems and cause server attacks.

And, what if the weakness is in your most critical system?

Yes, vulnerabilities in VPN protocols like IPSec are critical. It can even leak your private data.

That’s why, we often get requests to patch IPSec vulnerabilities as part of our Managed VPN Services.

Today, we’ll see the top IPSec vulnerabilities and how our Support Engineers fix them.


Few facts on IPSec

Basically, Internet Protocol Security (IPsec) is a secure network protocol suite that allows private communication. And, IPSec uses the Internet Key Exchange (IKE) protocol to ensure secure connection.

For this IKE process to work, there has to be a Security Association (SA) between the VPN peers. It uses key based method to encrypt and decrypt data. And, the flow of data across the VPN tunnel can happen only after this association.

Unfortunately, when there are flaws in any of the underlying protocols, it affects IPSec too.


Top IPSec vulnerabilities and their fixes

Vulnerability on any system makes your server an attack target.

But, how do you know about an IPSec vulnerability? Only after you are affected?

Definitely NO.

That’s where our Security Engineers have an upper edge. We keep regular track of security incidents in internet and get real time updates on any major flaws. Therefore, we always patch-up the vulnerability well in advance.

Now, let’s have a look at the top three IPSec vulnerabilities and how we act on them.


1. Man in the middle attack

As we already saw, IPSec VPN uses keys to identify each other. In this vulnerability, an attacker may be able to recover a weak Pre-Shared Key. Thus, this attack targets IKE’s handshake implementation used for IPsec-based VPN connections. Using these keys, it can decrypt connections. Ultimately, this will open the door to Man-in-the-middle (MitM) attacks. Eventually, this will result in leakage of VPN session data.

When any vulnerability happens due to a flaw in implementation, usually software providers itself will release a patch. For example, when this was reported in Cisco routers using IKEv1, they immediately released the patch for the vulnerability. To mitigate this attack, all we did was to ensure that the patch is correctly applied.


2. Password cracking

Similarly, another problem with IPSec happens with password cracking. Unfortunately, this happens with both IKEv1 and IKEv2 versions. When a VPN user enters a password, server first encrypts it and compare with stored values. If they match, the person gets access.

Unfortunately, using weak passwords in IPSec VPN makes it vulnerable to offline dictionary or brute force attacks.

That’s why, our Support Engineers always recommend customers to choose extremely complex passwords when they use IPsec through password-based logins. Additionally, we make sure that VPN uses cryptographically secure key values that can resist brute force or dictionary attacks.


3. Buffer overflow

Yet another IPSec vulnerability is buffer overflow vulnerability.

Buffer is nothing but a temporary storage space. At times, a program may forget buffer location and overwrites adjacent memory locations. This vulnerability happens due to a buffer overflow in the affected code area.

Here, attacker would first send UDP packets to the affected system. As a result, it allows attacker to execute arbitrary code and obtain full control of the system.

Again, this is a flaw in the implementation. For example, when this vulnerability was reported in Cisco ASA Software, they immediately came up with security fixes.

Here, the method of fix involved couple of steps. Our Support Engineers first check whether features like crypto mapIKEv1 or IKEv2 are configured on the device. Based on the output of the command, we always ensure that IKEv1 or IKEv2 is disabled on the affected system.

[Do you need advice on most secure VPN? We can guide you.]



In short, although IPSec VPNs are popular, it’s not free from vulnerabilities. Today, we saw top 3 IPSec vulnerabilities and how our Support Engineers patch them up.

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