Compromised EMudhra Intermediate Certificates

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Compromised eMudhra Intermediate Certificates

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Dennis Jackson

unread,9:01 PM (1 hour ago) 9:01 PM

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to dev-secur...@mozilla.org

Dear Mozilla Community,

On Saturday, October 17, at 20:06 UTC, Mozilla received a report from a community member that private keys associated with eight eMudhra intermediate certificates had been compromised. These keys could allow attackers to issue fraudulent HTTPS certificates for websites they do not control.

At 22:59 UTC, Mozilla completed the process of blocking the affected certificates in Firefox using OneCRL, Mozilla’s centralized list of revoked certificates which we introduced in 2015. OneCRL allows us to deliver this protection without requiring users to update or even restart Firefox.

We have since been working with the issuing CA, other root programs and downstream trust store operators to investigate the root cause, responsibly disclose the incident and help protect the wider ecosystem.

Today, 20th October, we are also releasing an update to the trusted certificates list in NSS which removes the root certificate used to sign these intermediates. Although this change is not necessary for Firefox, this helps protect other users of our trust store or third party derivatives who do not benefit from the protection of OneCRL. This change will impact the availability of some servers for those non-Firefox users until those servers move to new certificate chains.

We recommend all trust store operators take steps to protect their users. Mozilla cannot advise on the response suitable for any particular operator, but notes:

If clients will reliably check revocation information and fail-closed (reject) if it is absent, no action is needed. The CA has marked these certificates as revoked.

If the operator has a mechanism for blocking trust in particular intermediate CAs, the operator should block the certificates identified in the attached JSON impacted-intermediates.json and distribute that update to clients immediately.

Otherwise, the operator should consider whether removing trust in the roots which signed these intermediates is suitable. Mozilla has done so in its latest update to NSS (above). The roots which are known to chain to these certificates are listed in roots.json.

We believe transparency is essential to trust and will provide more information in this thread as soon as circumstances allow.

impacted-intermediates.json

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roots.json

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Arvid Vermote

unread,9:10 PM (1 hour ago) 9:10 PM

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to Dennis Jackson, dev-secur...@mozilla.org

Is there any information / details on the nature of the compromise available and whether it might impact / other CA’s might be vulnerable as well?