Why Shouldn’t You Overuse A Single Wildcard TLS/SSL Certificate?

Wildcard TLS certificates are a good example of an efficient solution that, if not properly handled, can quickly become insecure. On the one hand, wildcards are a straightforward approach to safeguard theoretically a limitless number of subdomains. On the other hand, the more wildcards that are employed, the greater the security risk they pose. That’s why many businesses have banned the use of wildcard certificates entirely because wildcards are insecure when used wrongly.

What is a TLS/SSL certificate with wildcard characters?

A wildcard TLS certificate is a single certificate that includes an asterisk (*) in the domain name field, allowing a single certificate to secure a domain as well as many subdomains. With a single wildcard certificate, administrators can theoretically safeguard an endless number of subdomains. As a result, wildcard certificates might help you be more efficient in your purchasing and distribution. However, just because a wildcard certificate may secure hundreds or thousands of subdomains doesn’t imply you should.

What are the security vulnerabilities associated with wildcard tls certificates?

While initially simple to set up, wildcard certificates can be difficult to locate and repair if something goes wrong, which is possible given that fraudsters can target and exploit wildcards. Unfortunately, making it easier to secure subdomains also makes it easier for attackers to compromise not only your main domain but all subdomains that use the same wildcard certificate.

In fact, the way some administrators utilize wildcards nowadays mimics certificate pinning, which we strongly advise against. Companies, for example, could utilize a single wildcard certificate in a thousand different places across several servers, including with external parties, because it is both efficient and insecure. If even one server is compromised, every domain that uses that certificate becomes susceptible, and the more agents you have handling your subdomains, the more you will need to share your private key, introducing significant risks. In a recent piece, we discussed why private keys should not be shared, but the worst-case situation is that hackers acquire access to the private key of a wildcard certificate, they might use it to set up any subdomain, secure it with the same wildcard certificate, and use it to spoof your legitimate brand in phishing attacks.

Because it can be applied in a secure manner without overwhelming workers, automation is the perfect answer for balancing security and efficiency. Automation achieves greater efficiency over your certificate inventory than a wildcard certificate. Forget about the headaches associated with excel files; current PKI systems automate certificate requests, renewals, validation, alerts, revocation, and much more, allowing you to simplify certificate lifecycle management, save time, and decrease risks. As a result, nine out of ten businesses are already implementing PKI automation.

When should you get a wildcard certificate?

You can still purchase a wildcard certificate if you need to secure multiple subdomains internally and securely. Wildcard certificates might help you save money and get started quickly. However, before obtaining a wildcard certificate, you should be aware of the security concerns and put in place controls and monitoring to ensure that your wildcard certificate cannot be used to its full potential. For example, you should minimize the use of wildcard certificates and use best practices to store and secure private keys.

Furthermore, Prima Secure can assist you in improving the security of your wildcard use with particular strategies if necessary. For example, we’ve assisted several of our customers in issuing a separate certificate signing request (CSR) for each wildcard. This will generate a duplicate certificate with a separate CSR for each issue, despite the fact that the wildcard is the same, which can give more separation and hence better security.

A multi-domain or Subject Alternative Name (SAN) certificate may also be a more secure choice. A SAN certificate, like a wildcard certificate, permits the certificate to cover various URLs but limits it to a specific list of URLs. Automation, on the other hand, is likely to be the best long-term answer for balancing security and efficiency throughout your certificate inventory.