Eight eMudhra Intermediate CA Keys Recovered From Their Own Certificates
The eight keys were one byte each and generated improperly by the CA itself, which means a root program's trust in eMudhra intermediates rested on private keys that could be read straight out of the certificates, and blocking them depends on revocation data that many clients do not yet apply.
Reporting from 1 source: GIGAZINE.
Eight eMudhra intermediate CA private keys were compromised, and the certificates chained to roots trusted by Mozilla, Microsoft, Apple, and Chrome programs and many downstream trust stores. The reporter signed messages with each key and notified root program teams on October 17, 2026. Firefox and Chrome blocked the certificates that day, Apple on October 19, Microsoft on October 20. eMudhra revoked the intermediates. The keys were recoverable because the CA generated them improperly, and all eight were one byte, one of them "4".
The intermediate certificates were created in April 2025, and the private keys could be recovered from them because eMudhra generated the keys improperly. According to information circulating on Hacker News, all eight were a single byte, and one was the value "4".
Revocation alone does not close the gap. Many clients do not recognize revocation information immediately, so software updates are needed before a client stops trusting the compromised intermediates. Mozilla, Microsoft, Apple, and Chrome distribute revocation data through OneCRL, CRLite, and CRLsets. An attacker holding the keys could impersonate any website or service until the intermediates were revoked. There are no Certificate Transparency log records for the intermediates in the relevant period, which affects clients that enforce CT.
Synthesized by Yomimono from the 1 cited source below, including Japanese-language reporting where cited, then editorially reviewed before publishing.