eMudhra Revokes 8 More CAs; Microsoft to Remove 10 Roots

Microsoft will remove all 10 remaining eMudhra roots from Windows, Edge and Azure on November 16, widening a certificate-trust crisis that began with a flawed ceremony involving 16 subordinate CA keys.

At eMudhra’s April 30, 2025 key ceremony, the company’s PKI team moved subordinate certificate-authority material between two vendors’ hardware security modules on a ceremony computer. The Indian certificate authority has now revoked another eight intermediate CAs, and peers will distrust the affected digital credentials.

At the ceremony, eMudhra generated 16 subordinate CA keys on Utimaco hardware security modules. The company planned to move them to Crypto4A modules for its delayed United States facility. To bridge the two vendors, its PKI operations team wrote its own Python script and switched off the source module’s FIPS-approved mode for that step.

How did one script line undermine the key ceremony?

The fault sat in a read-back step. eMudhra wrote in its Bugzilla incident report:

“For the ECDSA objects, a single line in that read-back truncated the private value to its leading byte, so the re-created object held a scalar below 256.”

The truncation left recreated ECDSA objects with a scalar below 256. Anyone could recover such a key by trying every possible number below that threshold.

The certificates remained public for about 18 months and passed two WebTrust audit cycles before a third party reported the flaw on 17 October.

The incident report also said that no part of the ceremony tested CA key strength or compared the certified key with the originally generated key. The browser Baseline Requirements do not require such a check.

In October, eMudhra said the keys were safe. An eMudhra engineer said:

“The RSA issuers went through a different path as per our assessment of the code and are therefore not impacted.”

The company has since withdrawn that assurance after finding that the keys’ secret parts sat in the ordinary memory of the ceremony computer while being moved, outside the protection of the hardware modules.

What does the trust withdrawal change for enterprises?

EMudhra’s roots shipped in trust stores used by Windows, macOS, Firefox, Chrome and major Linux distributions. As a result, Australian systems trusted its intermediates by default.

Google and Mozilla will let existing, older certificates expire. Apple had already blocked the compromised certificates in Safari, Mail and apps built on its frameworks in October. Yet command-line tools such as curl and git continued trusting them until macOS versions 27.2.1, 26.7.3 and 15.8.3 removed the roots from the system certificate file.

EMudhra said Apple would end trust in all of them on November 30. Microsoft’s action covers all 10 remaining roots in Windows, Edge and Azure from November 16.

EMudhra is leaving the public TLS business, with all issuance from its older G1 hierarchy due to stop by 10:59am AEDT on 17 November.

For enterprises, the practical change is a hard expiry schedule, not merely a browser warning. Organizations need to identify certificates and services that still chain to eMudhra, including command-line clients and build systems, before their trust disappears.

• November 16: Microsoft removes all 10 remaining eMudhra roots from Windows, Edge and Azure.
• 10:59am AEDT on November 17: eMudhra stops all issuance from its older G1 hierarchy as it exits public TLS.
• November 30: Apple’s broader trust withdrawal follows its October blocks in Safari, Mail and framework-based apps.

The practical takeaway is blunt: eMudhra’s public TLS operation is ending, and its remaining trust footprint now has a fixed shutdown calendar.