Global Browsers Block eMudhra Certificates After Weak Key Generation Flaw

On April 30, 2025, Bengaluru-based certifying authority eMudhra Ltd generated eight intermediate certificates with private keys far weaker than industry standards. Because these intermediates sit between root CAs and end-entity certificates, possession of any one key would allow an attacker to issue certificates for any website or software program. Major browsers and OS vendors (Google, Mozilla, Apple, Microsoft) responded by revoking the affected certificates and blocking them from their root stores.

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Web browsers trust a limited set of certificate authorities (CAs) that sign digital certificates proving a site’s identity. eMudhra is the sole Indian root CA listed in the trust stores of the four major browsers, and its intermediates were used to sign certificates for government portals, banks and IoT devices. A failure at a single CA can compromise authentication for organisations that never dealt directly with that CA.

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• Compromised intermediates: 8

Hindustan Times

• Key values: 4, 56, 66, 115, 155, 156, 230, 237

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• Intended use: 6 TLS certificates, 2 code-signing certificates

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• Key entropy: Supposed to exceed the number of atoms in the observable universe; the actual keys fell within the range 1-256.

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• eMudhra said a flaw in its Key Generation Ceremony produced a second set of weak keys, which were mistakenly published to browser root stores. The company asserts its infrastructure was not compromised and that its digital-signature and eSign services remain unaffected. Revocation and containment procedures have been initiated.

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• CERT-In warned that the keys could be recovered “almost instantly” and could be used to intercept communications, leading to credential theft and financial fraud. It urged government departments, ISPs, software vendors and website administrators to update trusted-certificate lists.

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• Browser vendors have removed the eight intermediates from their root programs, preventing browsers from accepting certificates signed with the weak keys.

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Security researchers noted that many IoT devices and legacy systems cannot be patched easily, making the cleanup “enormous.”

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• Scope of impact: MeitY describes the effect on Indian digital services as brief and limited, while CERT-In highlights the potential for widespread credential theft.

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• Evidence of exploitation: No public record confirms that the weak keys were used in attacks, but forged certificates could bypass detection on systems that do not check Certificate Transparency logs.

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• Audit coverage: eMudhra’s root certificates have undergone independent WebTrust audits for two consecutive years, but the ministry clarifies it was not involved in the audit of the specific key-generation process that failed.

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• “As this incident enables even technically unsophisticated individuals to easily recover the private keys for these intermediates, the impact of this incident could not be higher,” — Mozilla, cryptography engineer

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• “This isn’t just about eight compromised keys. It’s about the global internet’s chain of trust,” — Yash Kadakia, CTO, Security Brigade

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MeitY’s special team will continue investigating the root cause. Browser vendors are ensuring all affected certificates are fully revoked, while security firms advise organisations to audit their trusted-certificate stores and prioritize updates for devices that cannot receive frequent patches. The cleanup effort will focus on legacy routers, payment terminals and other embedded systems.

The Hindu