Microsoft has confirmed that it has revoked trust in a Malaysian certificate authority (CA) that issued 22 certificates with weak 512-bit keys, and certificates without the appropriate usage extensions or revocation information.

As revealed by SC Magazine last week, Microsoft's group manager of response communications, Jerry Bryant, said there was no indication that any certificates were issued fraudulently, but the weak keys had allowed some of the certificates to be compromised.

In an update, Bryant said: “Today we released Security Advisory 2641690 to notify customers that we revoked the trust of DigiCert Sdn.Bhd in an update that moves two Intermediate Certificate Authorities' certificates to the Microsoft Untrusted Certificate Store.

“We made this decision after Entrust, a CA in the Microsoft Root Certificate Program, notified us that one of its subordinate CAs issued 22 certificates with weak keys, a violation of the program requirements. At this time, there is no indication that the certificates were issued fraudulently, but with this update, we are proactively protecting customers from potential issues.

“There is no action for customers who have enabled Automatic Updates as the update, which applies to all supported versions of Microsoft Windows, will be downloaded and installed automatically.”

DigiCert Sdn. Bhd (Digicert Malaysia) is a subordinate CA under Entrust and Verizon (GTE CyberTrust), and is not related to DigiCert Inc, which is a member of the Windows Root Certificate Program.