An investigation into India's certification authority eMudhra has uncovered compromised private keys that could undermine the security of more than 60 million digital certificates issued by the company.
The incident, reported to Mozilla on October 17, 2026, creates risks for HTTPS connections because attackers could use the exposed keys to forge certificates and impersonate legitimate websites.
Dennis Jackson, a member of Mozilla's cryptography engineering team, disclosed the incident in a post on Tuesday, October 20, 2026.
He said Mozilla received a report from a community member concerning eight compromised eMudhra intermediate certificate keys, prompting a response from browser developers and other software projects.
Forgery risk and browser response
The compromised keys could enable fraudulent certificates that appear to authenticate websites controlled by legitimate operators.
According to Cloudflare, an attacker could forge a certificate for any domain and impersonate servers to intercept or modify network traffic.
Mozilla, Google Chrome, and Apple have taken steps to address the vulnerability by ensuring their browsers no longer trust the affected certificates after users install the relevant updates.
Jackson also reported that eMudhra had revoked the certificates, while multiple free and open-source software projects released updates to stop recognizing certificates issued through the compromised authority.
Despite those measures, certificates signed using the compromised keys may remain in circulation, and some services could continue relying on them.
Organizations that use eMudhra certificates may need to inspect their systems to identify affected certificates and determine whether further remediation is necessary.
Developer Geoffrey Huntley has offered guidance on automating that process.
Security researcher Scott Helme found that some of the compromised private keys were extraordinarily simple numeric values.
His analysis indicated that the keys could be recovered from publicly available certificates with minimal effort.
Helme described one of the recovered keys in a post about the incident.
"is the number 4." Helme wrote.
He provided further details about the recovered values, emphasizing that the weakness was not limited to a single key.
"Not a number that starts with 4, or the number 4 followed by a few hundred random digits, just, 4...
Another one is 56, and another is 115.
I know, because I recovered all of them from their public certificates on my laptop just now, and it took less than a second," Helme wrote.
Other researchers identified additional private keys with numeric values of 66, 155, 156, 230, and 237.
Such predictable values fall far short of the randomness required for secure cryptographic keys and make brute-force recovery substantially easier.
Helme explained the scale of the weakness by comparing the recovered values with the expected security of a P-384 private key.
"A P-384 private key should be a random 384-bit number, which gives you 2³⁸⁴ possibilities (or roughly 10¹¹⁵), so nobody is ever going to search that."
Helme wrote.
The compromise raises questions about the security practices used to generate and protect keys at an authority responsible for issuing millions of digital certificates.
At the time of The Register's report on October 20, 2026, eMudhra had not responded to the publication's inquiries about the incident or its security practices.
