The private keys associated with eight intermediate certificates issued by Indian Certificate Authority (CA) eMudhra have been compromised, and root programs and trust stores have begun blocking them.
The certificate was issued in April 2025, and some compromised keys could allow an attacker to create a fraudulent certificate and impersonate a website.
This October 17th. Mozilla And Google Block certificates in Firefox and Chrome. Apple and Microsoft blocked them on October 19 and October 20, respectively. Sectigo has taken the retraction process as well, and Cloudflare patched its service.
eMudhra has removed the compromised credentials, and the issue has been communicated to trusted merchants.
“The private keys for these certificates are generated with insufficient randomness (ie, weak cryptographic entropy), allowing anyone to forge a trusted HTTPS certificate to impersonate any website to clients who have not yet trusted those CAs,” Google explained.
Even if the certificate is intercepted and revoked, some customers may need software updates to ensure that compromised intermediaries cannot be trusted.
Mozilla’s Dennis Jackson has published A tool to check if a client still trusts a compromised certificate. He also explained that private keys are generated incorrectly and can be derived from certificates.
In fact, Jackson warned that some people have taken the keys independently, because the process is relatively easy and fast.
“Private keys are effectively all zeros except for the last byte. They are instantly recoverable through a child-sized giant tape decryption process,” Jackson said. said.
There appears to be no evidence in the Certificate Transparency (CT) log that the keys were used maliciously before the revocation, but not all clients enforce CT, and attackers may use them to impersonate those clients.
According to eMudhra, a flaw in the script used during the key generation ceremony created a second, weaker key pair, which was mistakenly used to generate the certificate signing request because its label was identical to the original key.
“Some additional context – these issuers were created to export to our US and European data centers to solve data sovereignty issues for some of our customers (but never ended up operating in production except for one),” said CA.
“There were human errors in many stages of the process that caused major flaws in the critical life cycle integrity process for this KGC. We are now digging deeper for code flaws, process gaps, and manufacturer/checker controls specific to this issue. In the next week, we will review every major ceremony we have done,” eMudhra added.
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