eMudhra Exits Certificate Business After Weak Key Incident

Indian certificate authority eMudhra has announced its withdrawal from the global SSL/TLS certificate business. The decision follows a security incident in which researchers identified critically weak private keys in several of the company’s intermediate certificates. Major web browsers, including Chrome, Firefox and Safari, subsequently blocked these certificates to protect users from potential impersonation attacks.

Root cause

The vulnerability stemmed from a flaw in the key generation ceremony held in April 2025. Instead of producing complex, random 384-bit numbers, the process generated trivial integers. Cybersecurity researcher Scott Helme publicised the issue, noting that one private key was simply the number four. Other affected keys were identified as 56 and 115. eMudhra attributed the error to a specific step in the ceremony procedure.

Attack path

Weak keys allow attackers to derive the corresponding public certificates without authorisation. According to Google and Mozilla, this could enable the issuance of fraudulent HTTPS certificates for domains the attacker does not control. Cloudflare explained that because these certificates were widely trusted, an attacker could impersonate servers. This would allow the interception or modification of traffic between users and websites.

Affected versions

The issue affected eight intermediate certificates issued by eMudhra. These certificates were trusted by major browsers and operating systems prior to their revocation. The company stated that the flawed certificates were created during the April 2025 ceremony and remained undetected for 18 months. They survived two independent audits before being identified through reverse engineering by a researcher.

Mitigation

eMudhra revoked the affected certificates within 14 hours of discovering the weakness. The company’s chairman, V. Srinivasan, stated that there were no known compromises or data breaches resulting from the incident. Major browser vendors blocked the certificates to prevent their use. India’s Ministry of Electronics and IT is investigating the matter, while CERT-IN issued warnings about potential credential theft and fraud.

Why it matters

Certificate authorities rely on the secrecy and complexity of private keys to establish trust. When keys are weak or predictable, the entire chain of trust collapses. Teams usually monitor Certificate Transparency logs to detect unusual issuance patterns. In this scenario, the lack of randomness meant that any observer could mathematically derive the keys. This undermines the fundamental security model of HTTPS, allowing attackers to create valid-looking certificates for any domain. Understanding this highlights why rigorous, auditable key generation procedures are essential for any organisation issuing digital credentials.

What to do and how to stay safe: eMudhra

• Review your internal certificate inventory to ensure no eMudhra-issued intermediate certificates are still trusted in your root store.
• Monitor browser console logs and certificate transparency feeds for any unexpected certificate issuances for your domains.
• Verify that your security tools are updated to recognise the revoked certificate serial numbers and block associated traffic.
• Once the vendor provides an update or further guidance, review your own key generation practices to ensure adequate entropy.

Step-by-step guide: Password Policies Examples That Reduce Password Fatigue

General security guidance from the Vector Bulletin newsroom. It is not confirmed advice from the organisations named in this story.

Frequently asked questions

Did eMudhra confirm any data breaches?

No, eMudhra’s chairman stated there were no compromises or data breaches as a result of the weak keys.

How long were the weak certificates in use?

The certificates were created in April 2025 and remained undetected for 18 months before discovery.

Which browsers blocked the certificates?

Firefox, Apple Safari and Chrome blocked the certificates due to the security risks posed by the weak keys.