- Shares of eMudhra Ltd. dropped 20% after distrust in some certificate authorities.
- The issue involves eight intermediate CAs created under eMudhra’s ECC root in 2025.
- A flaw in key generation produced weak keys published to browser root stores.
Shares of eMudhra Ltd. fell 20% to Rs 432 apiece on Wednesday after reports that some of its certificate authorities, used in its global TLS business, were being distrusted.
In a statement issued on Wednesday, the Bengaluru-based digital trust company said the matter concerns eight of its intermediate certificate authorities that were trusted as part of its global TLS business.
These issuing CAs were created under eMudhra's ECC root during a key generation ceremony held on April 30, 2025, using FIPS 140-2 Level 3 hardware security modules. According to the company, a flaw in the ceremony caused a wrap/unwrap step to produce a second set of weak keys alongside the original strong keys. The weak keys were the ones published to browser root stores.
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Last weekend, an independent researcher found that the weak keys could potentially be reverse-engineered, possibly using AI-assisted techniques. The researcher reported the issue to the major root programmes run by Apple, Google, Microsoft and Mozilla.
eMudhra said it is still working to establish the root cause. The roots and issuing CAs had cleared independent audits for two consecutive years and had been in browser trust lists since mid-2025, the company said.
What Went Wrong
A certificate authority's private key is meant to be a random number so large that it cannot be guessed. In eMudhra's case, Mozilla security researcher Dennis Jackson wrote in the incident report that the affected keys, created on April 30, 2025, all used integers below 256, which lets them be recovered almost instantly. One of them, for the EM OV TLS CA – G3C certificate, had a value of just four. An attacker could recover each key by testing at most 255 possible values.
That means anyone holding one of these keys could have issued a certificate for any website, and browsers would have accepted it. An intermediate CA signs the certificates that websites present, which is why the flaw was treated as serious.
The researcher, known only as Wayne, proved the problem by using the eight private keys to sign a message. Mozilla recovered the keys on its own in under two hours.
eMudhra's explanation, given in Mozilla's public incident record, is that a flaw in its ceremony script created a second, weak key pair on the HSM during a key-wrapping test. The weak keys had labels similar to the intended keys, and they were the ones used for the certificate requests. The company also wrote that there were human errors in multiple steps of the process.
one of eMudhra's CA private keys was literally 4. google and mozilla acted within hours. MeitY's CCA licenses eMudhra. CERT-In hasn't issued a public advisory till now. eMudhra works as a technology provider for government project. literally zero accountability.
— nisarga (@ni5arga) October 21, 2026
How The Browsers Responded
The Chrome Root Program received the report at 18:05 UTC on October 17 and had a block on the six TLS intermediates in place by 19:45 UTC. The certificates have been blocked in Apple devices since October 19 and on Microsoft platforms since October 20. eMudhra revoked the certificates on October 18, and Sectigo, which had cross-signed them, followed on October 19.
The response did not stop at the eight certificates. Mozilla removed eMudhra's emSign ECC Root CA - G3 from its trust store on October 20. Google said the same root's removal is expected to reach all devices relying on the Chrome Root Store on October 27. Google said that, given the seriousness of the incident, it is closely investigating whether eMudhra's remaining CA certificates should stay in the Chrome Root Store.
eMudhra said it is still working to establish the root cause. The roots and issuing CAs had cleared independent audits for two consecutive years and had been in browser trust lists since mid-2025, the company said.
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No Breach, Says Company
eMudhra said its infrastructure was not compromised, no data was breached, and all physical and logical security controls remained intact.
The company said the incident has no connection with its Indian Digital Signature Certificate and eSign businesses. These run on infrastructure that is completely separate from the global TLS business and are operating normally.
The affected global TLS business accounts for about 1% of eMudhra's revenue, the company said. It acknowledged, however, that the episode could carry reputational risks that cannot be quantified.
eMudhra said it is working directly with potentially affected customers to issue replacement certificates so that critical services are not disrupted. It is also working with the root programmes as its root-cause investigation continues.
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