eMudhra intermediate CA certificates compromised: What happened, who is affected and what users need to know | Explained

CERT-In has issued a security advisory warning that eight intermediate certification authority (CA) certificates associated with eMudhra have been compromised, raising concerns about the security of encrypted internet communications and the authenticity of website certificates.

The advisory, CIAD-2026-0050, issued on 21 October 2026, says the incident involves weak cryptographic private keys that could potentially allow attackers to issue fraudulent TLS certificates, impersonate legitimate websites and intercept or modify encrypted communications.

The Indian Computer Emergency Response Team (CERT-In) said eMudhra Limited, an India-based certification authority, reported that private keys associated with eight intermediate CA certificates in its public key infrastructure (PKI) had been compromised.

The development has prompted browser vendors, including Google and Mozilla, to take steps to block the affected certificates and prevent their misuse.

However, eMudhra has stated that none of the affected intermediate CAs had issued end-entity certificates and that the incident was limited to the intermediates. It also said the compromise did not involve its root CA private keys or other intermediate CAs.

What happened to eMudhra’s certificates?

According to CERT-In, the affected private keys were generated using insufficient cryptographic randomness.

The P-384 elliptic-curve private keys had exceptionally small values, making them potentially recoverable almost instantly.

In a secure certificate system, private keys are meant to remain secret and computationally difficult to derive. Weaknesses in how these keys are generated can undermine that protection.

An intermediate CA acts as a link between a trusted root certification authority and the certificates used by websites and other services. If an attacker obtains an intermediate CA’s private key, they may be able to issue certificates that appear to come from a legitimate certification authority.

Such certificates could potentially be used to impersonate websites or facilitate attacks on encrypted connections.

CERT-In warned that attackers exploiting the compromised keys could intercept or modify communications, potentially exposing sensitive information such as financial data.

The compromised keys could also be misused to sign malicious software, making it appear to originate from a trusted publisher.

What have Google and Mozilla done?

The advisory outlines measures taken by two major browser vendors to limit the risks associated with the affected certificates.

Mozilla: Mozilla blocked the six affected TLS intermediate certificates through its OneCRL certificate block list. It released Firefox 158.0.1 for desktop and Android, Firefox ESR 115.45.1 and Firefox ESR 153.5.1 to protect users whose configurations prevent them from receiving OneCRL updates.

Mozilla also updated the trusted certificate list in Network Security Services (NSS) 3.131.1 to remove the root certificate that signed the affected intermediates.

Google: Google blocked the public keys of the affected TLS intermediates through a Certificate Revocation List Set (CRLSet) update.

Google also announced the removal of emSign ECC Root CA – G3 from the Chrome Root Store, scheduled for release to living Chrome Root Store users on 27 October 2026.

The changes are intended to protect applications and devices that do not receive or enforce intermediate certificate revocation information.

What does this mean for ordinary internet users?

TLS certificates help browsers establish encrypted connections with websites. They also help verify that users are communicating with the intended website.

If the certificate system is compromised, attackers may be able to impersonate legitimate websites or interfere with encrypted communications under suitable attack conditions.

However, the advisory does not establish that users’ banking details, passwords or other personal information have already been stolen.

It also does not say that all eMudhra certificates are compromised.

The reported incident concerns eight intermediate CA certificates, with eMudhra stating that no end-entity certificates were issued by the affected intermediates.

For ordinary users, the immediate precaution is to keep browsers, operating systems and applications updated so that the latest certificate restrictions and security protections are applied.

What should website owners and organisations do?

CERT-In has recommended several measures for organisations, website administrators and technology service providers.

• Install security updates: Update Firefox, Firefox ESR, other affected browsers, applications and operating systems to the latest available security releases.
• Update certificate trust stores: Ensure that operating systems, applications, servers and devices receive the latest certificate revocation and distrust information.
• Review certificate chains: Identify certificates and services that depend on the affected intermediate CAs or emSign ECC Root CA – G3.
• Replace affected certificates where necessary: Obtain replacement TLS certificates from an unaffected and trusted certificate hierarchy. Administrators should also replace legitimate certificates chaining to the affected root if clients will no longer trust it.
• Verify TLS certificates: Check certificate chains, issuers, validity periods and revocation status. CERT-In has warned against bypassing certificate validation warnings or disabling certificate verification.

CERT-In has also advised organisations to monitor Certificate Transparency logs for unauthorised certificate issuance and strengthen CA key management practices through secure random number generation, hardware security modules and regular reviews.

The advisory highlights how weaknesses in certificate infrastructure can create security risks beyond a single website. While browser vendors have introduced protective measures, keeping software updated and ensuring that certificate trust chains remain valid will be important for users and organisations relying on encrypted communications.