Root programs and trust stores across global browsers and operating systems have begun blocking eight intermediate certificates issued by the Indian Certification Authority (eMudhra), following confirmation of a leak or severe weakness in their associated private keys that allows them to be easily recovered.
The certificates in question were issued in April 2025, and Google explained that the private keys were generated with an insufficient amount of randomness and weak cryptographic entropy, allowing anyone to forge trusted HTTPS certificates and impersonate any website against clients who have not yet removed trust in those certificates. In response, major companies such as Mozilla and Google rushed to block the certificates in Firefox and Chrome in mid-October, followed by Apple and Microsoft in subsequent days, as well as similar actions taken by Sectigo and Cloudflare.
Ease and Speed of Recovering Weak Keys
Researcher Dennis Jackson from Mozilla published a tool to check whether systems still trust the compromised certificates, explaining that the private keys were generated incorrectly, consisting of zeros except for the last byte. Jackson confirmed that several individuals were able to independently and very quickly recover the keys using the baby-step giant-step algorithm.
For its part, eMudhra explained that the flaw is due to an error in the script used during the key generation ceremony, which resulted in the creation of a second, weaker key pair that was mistakenly used to generate certificate signing requests due to its similarity in naming to the original keys. The company noted that these issuers were originally created for export to data centers in the United States and Europe to solve customer digital sovereignty issues, affirming that they were never operational in production except in a single case.
What Changes in Practice?
Although there is no evidence in Certificate Transparency (CT) logs that these keys were used maliciously prior to their revocation, some customers may need software updates to ensure that these intermediate certificates do not remain trusted by them. eMudhra is currently conducting deeper reviews of code vulnerabilities and operational gaps, pledging to re-verify every key ceremony it has performed over the coming weeks.