We recently renewed our Nginx webserver's Thawte SSL certificate. Previously we'd been using SHA1 as the signing algorithm, but this time used SHA256 which leads to a new root certificate known as "thawte Primary Root CA - G3" (this can be found on their website - not enough rep to post the link).

Since rolling out we started getting calls from customers using OS X about getting the error "This certificate was signed by an unknown authority" when browsing to https page.

Thawte's certificate checker is perfectly happy with our installed certificate chain: https://ssltools.thawte.com/checker/views/certCheck.jsp (we have our certificate, plus "thawte Extended Validation SHA256 SSL CA" intermediate in the pem file)

After testing, we found errors occurs under Safari, Opera and Chrome on OS X os all versions. Firefox was OK under OS X (I believe it ships with it's own certificate trust store). All browsers seem OK under Windows.

When we checked the OS X Access Keychain, we found the thawte Primary Root CA - G3 WAS installed, but somehow the browser wasn't managing to complete the chain.

Here's a test site (not ours) using the same intermediate and root which exhibits exactly the same symptoms under OS X:


Can anyone explain why OS X is not recognising the root CA for this site as being trusted when it is installed in the Access Keychain of OS X 10.9 by default?

  • I have seen this issue in the wild too, with OSX and a Thawte issued cert. For me it appears to be resolved, possibly by an OSX update in the past few days
    – carpii
    Jan 23, 2015 at 12:38
  • Same this for DigiCert Intermediate Certificate. I am seeing error on Apple MAC while using this certificate
    – user275532
    Mar 10, 2015 at 19:58
  • I have similiar problem with the G2 (not G3) certificate from within OSX and Debian/Ubuntu console. The information on Thawte website not up to date either..
    – Daniel W.
    Jan 11, 2016 at 10:23

2 Answers 2


Just spoke w/ Thawte support via chat and they have confirmed it's a problem and an open case w/ Apple (since July 31, 2014) on the issue. No response / ETA on a fix as of yet.

  • 1
    Thawte just emailed me with the same info that the root cert in question is not valid for EV certificates. Looks like using a SHA256 cert + the Thawte SHA1 root is the interim solution until Apple fix it. Thanks.
    – David QC
    Sep 25, 2014 at 8:36
  • FYI, GlobalSign's SHA256 chain link seems to be fine on MacOS.
    – DaveM
    Sep 25, 2014 at 14:23

On September, 17th 2014, the Primary Root CA - G3 (intermediate with a SHA-256 signature) was still not accepted by latest Mac operating systems.

Thawte submitted an Apple Bug Number 17095623 in order to have them fix this issue.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.