Browsers Block eMudhra Certificates After Key Flaw

Bengaluru-based digital trust company eMudhra generated eight intermediate certificate authority (CA) private keys with minimal randomness, which attackers could recover almost instantly. 

Six of the affected certificates were authorised to issue TLS certificates for websites, potentially allowing attackers to impersonate domains they did not control on systems that still trusted the compromised keys. The other two were intended for code signing.

The incident came to light when a security researcher, Wayne, whose identity remains anonymous, demonstrated control of the eight private keys by using them to sign a message.

Google’s Chrome Root Program received the report and blocked the public-key hashes of the six TLS-issuing intermediates. 

Mozilla received its report and had protections available to Firefox users with standard configurations. Its investigation found that all eight affected keys used P-384 elliptic-curve cryptography but had private-key values below 256. 

P-384 keys should be selected unpredictably from a vast range of possible values. 

In this case, an attacker could recover each private key by testing at most 255 possible values. 

The vulnerability lay in the key-generation process, not in a failure of the underlying cryptographic algorithm.

Intermediate CAs sit between root certificates and the certificates websites present. 

Browsers trust these intermediaries to issue certificates that establish a website’s identity. 

Anyone with a compromised TLS-issuing key could create a fraudulent certificate for a domain they don't control. 

If the attacker could also intercept or redirect a victim’s connection, they could use the certificate to impersonate the legitimate website or intercept and modify traffic.

Google and Mozilla have blocked the affected certificates in their respective trust systems, but protection across the wider internet also depends on other software and trust stores receiving equivalent updates.

eMudhra said it generated the certificates during a key-generation ceremony on April 30, 2025. 

The company said it had deployed only one of the eight affected intermediates in production, and none had issued end-entity certificates. It said internal analysis and publicly available Certificate Transparency records supported this finding.

eMudhra added that the incident did not affect its root CA private keys or other intermediate CAs. Its investigation into the incident and its security controls is ongoing.

“This incident has no impact on customers using our enterprise applications, digital signature services, or other electronic signature solutions,” said the company in a post on X. 

Founded in 2008, eMudhra provides public-key infrastructure (PKI), digital signatures, certificate management, authentication and identity and access management products. 

Its emSign business issues digital certificates, while its emSigner platform supports enterprise digital-signature and document-workflow processes. 

The company lists organisations including Infosys, Airtel, Kotak Bank, Tata Steel, Amazon, ICICI Bank and Cisco among its emSigner case studies. These enterprise-software relationships are separate from the affected emSign certificate infrastructure.

eMudhra shares fell 18% in early trading sessions on NSE on October 21.