DigiCert Blog

Heartbleed and the Problem of NotBefore Date

There are several online Heartbleed detection tools that rely solely on checking the NotBefore Data. There are major flaws with this approach to Heartbleed vulnerability that administrators should consider.

Fixing Heartbleed Vulnerability

It is standard practice among Certificate Authorities, when re-keying an SSL certificate, to keep everything in the cert the same except for information related to the actual keys that have been changed.

That includes the validity dates, which has become an issue in the past day or so as at least one tool to test for Heartbleed vulnerability is looking at the NotBefore field (the beginning date) of a certificate to determine if it was issued before or after the Heartbleed fix on Monday.

Why you can’t rely on NotBefore Date

There are a couple major flaws with this approach to Heartbleed vulnerability scanning:

  1. A site could have a new certificate, but if they installed it before patching their OpenSSL installation, it is subject to the same vulnerabilities as the previous certificate.
  2. Very few certificates that have been re-keyed will show a new NotBefore date.

SSL Encryption is at the core of online data security. As such, DigiCert has released a free Certificate Inspector. The Certificate Inspector cloud-based certificate management platform allows administrators to review all certificates used by their servers and automatically ensure that they are not vulnerable to Heartbleed and a number of other critical security vulnerabilities. Certificate Inspector’s unique algorithm assigns grades to your certificates and their implementations, and provides an easy to follow list of remediation actions.

We have contacted the makers of the one tool we are aware of and urged them to change their methodology to be more in line with the actual practices of CAs. We urge the makers of any other similar tools to do the same. Until then, many sites that have patched the security hole will continue to return false positives.

Check the security of any site online

Users can also review individual sites for Heartbleed protection by using the DigiCert Certificate Checker tool for free on by going to digicert.com/help. The DigiCert Certificate Checker allows users to check the security for any site on the Internet using an SSL Certificates from any Certificate Providers. The checker also includes Heartbleed Detection and ensures that sites are not vulnerable to weak keys or other server security vulnerabilities.

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About Jeff J. Snider

Jeff J. Snider is DigiCert's VP of Community, having previously headed up the programming team as VP of Development. Jeff has been at DigiCert since 2004, and he knows a lot more about baseball than a well-adjusted person should. Sadly, his attempts to change DigiCert's name to "DodgersCert" have been rebuffed.