I've been having this problem for a couple of months everytime I went to https://github.com I would get a SSL Certificate was expired error. I only encountered this error in Google Chrome on a Mac. I did not have this problem in any other browser like Firefox or Safari.
I could not figure how to fix it. I tried uninstalling/reinstalling Chrome. Uninstalling all extensions. Nothing worked.
I started to notice the problem on more and more sites since the initial github issue surfaced. So I finally had to do some research.
I finally found a blog post on the Digicert website that acknowledges the problem:
On July 26,2014 at 12:15 PM, some customers and users on sites secured by DigiCert reported that they were getting an untrusted certificate error.
The problem is related to a locally installed legacy intermediate certificate that is no longer used and no longer required for the certificate installation. The problem can affect any client platform with a locally cached or installed intermediate certificate.
Digicert confirmed the problem existed in:
- Clients (mainly OS X) with the expired intermediate installed in their local keychain.
- Server-to-server connections on Windows environments, where one server still has the legacy certificate installed.
Here is a description of the problem:
Expired Legacy Intermediate Certificate
The expired certificate in question is the “DigiCert High Assurance EV Root CA” [Expiration July 26, 2014] certificate. This temporary intermediate certificate was used in years past as part of a compatibility chain for older devices.
This certificate has not been used for over three years and is unnecessary for installations.
For instructions on removing the expired certification go to the digicert blog post and follow the instructions. Once I removed the certificate from the Keychain access I was able to go to sites normally again.