EIGHT intermediate certificates issued by Indian certificate authority eMudhra have had their private keys compromised, with root programs and trust stores moving to block them. The certificates were issued in April 2025, and attackers could potentially forge trusted HTTPS certificates to impersonate any website if clients had not yet removed trust in those CAs. Mozilla and Google blocked the certificates in Firefox and Chrome on 17 October 2026, followed by Apple and Microsoft on 19 and 20 October respectively.
Sectigo revoked the certificates, and Cloudflare patched its services in response. eMudhra revoked the compromised certificates and notified downstream trust stores of the issue.
The private keys were generated with insufficient randomness, enabling near-instant forgery of trusted certificates on unpatched clients. Security researchers have noted that several copies of the keys have been retrieved; the keys are effectively all-zeroes apart from the last byte and can be recovered rapidly via the baby-step giant-step discrete log method.
While there is no evidence in Certificate Transparency logs that the keys were used maliciously before revocation, not all clients enforce CT, leaving potential for abuse. eMudhra has indicated that a flaw in the key-generation script produced a second, weaker key pair used to create certificate signing requests because of similar labels to the original keys.
The CA says these issuers were intended for data‑sovereignty reasons for certain customers and that they are reviewing the key ceremonies and controls, with a re-verification planned over the coming week.