eMudhra Revokes Eight Weak Intermediate CA Certificates

On October 17, 2026, security researcher Wayne discovered that private keys belonging to eight eMudhra intermediate Certificate Authorities (CAs) were weak. eMudhra said on October 21 that a script flaw during a Key Generation Ceremony on April 30, 2025, had generated and mistakenly published a second set of weaker keys. Insufficient randomness made the P-384 private keys recoverable by testing a small number of possibilities.

Public Key Infrastructure and Certificate Authorities

A Certificate Authority is an organisation that issues digital certificates linking a public key to an identified entity, such as a website. In Public Key Infrastructure (PKI), intermediate CAs issue certificates under a root CA, creating a chain used by browsers and operating systems to verify certificates. A compromised CA private key can be used to create certificates that appear trusted within that chain. The weak eMudhra keys could have enabled attackers to forge trusted certificates for legitimate websites. Such certificates could be used to impersonate websites and intercept encrypted communications if accepted by clients. eMudhra revoked the eight certificates and stopped issuing new certificates under its G3 root; it stated that most affected intermediate CAs had not been used in production.

Cryptographic Keys and TLS

P-384 is an elliptic-curve cryptographic curve with a 384-bit field size, used in public-key cryptography. Private keys must be generated using sufficient randomness because predictable values can make key recovery possible. Transport Layer Security (TLS) is a protocol used to secure communications between clients and servers; digital certificates support authentication of the server during a TLS connection. Mozilla, Google, Apple and Microsoft, along with internet infrastructure provider Cloudflare, blocked the compromised certificates and introduced emergency fixes around October 19–20, 2026. eMudhra said its Indian Digital Signature Certificate (DSC) and eSign businesses use separate infrastructure and were not affected. On October 21, 2026, the company’s shares reached a 20% lower circuit following reports of distrust in some intermediate CAs used in its global TLS business.

Certificate Revocation and Trust

Certificate revocation is the withdrawal of a digital certificate before its scheduled expiry. Browsers and operating systems maintain mechanisms to reject certificates that are revoked or no longer trusted. CA root and intermediate certificates form distinct levels in the certificate trust hierarchy.

Important Facts for Exams

• A digital certificate binds a public key to an identity and is digitally signed by its issuing CA.
• TLS provides authentication and encryption for data exchanged between networked systems.
• P-384 is also known as secp384r1, an elliptic-curve cryptographic standard.
• A lower circuit is a stock-exchange price limit that restricts a security’s trading decline during a session.

eMudhra stated that the Indian DSC and eSign operations were unaffected because they run on separate infrastructure. The incident concerned intermediate CAs used in the company’s global TLS business.