By Hamza Faisal
A security researcher has reported that the private keys for eight intermediate certificate authority (CA) certificates belonging to India's eMudhra are compromised — a serious incident, because an intermediate CA signs the certificates websites present, so anyone holding one of these keys could mint a trusted certificate for any website on the internet.
The report landed with Apple, Google, Microsoft, Mozilla and eMudhra itself on the evening of Saturday, October 17. After Google's Chrome Root Program verified the findings, Chrome and Firefox blocked all eight certificates within hours.
The keys were barely keys at all
What turned this from bad to surreal is the nature of the keys themselves. Security researchers recovered the private keys from the certificates' public components in under a second — because the supposedly random secrets were tiny single-byte numbers: 4, 56, 66, 115, 155, 156, 230 and 237.
One of them is literally the number 4. These are ECC certificates on the P-384 curve, where a private key should be a random number of about 116 digits. A key of 4 is the cryptographic equivalent of locking the vault with a piece of string.
The eight intermediates include six used to issue website certificates (DV, OV and EV, two generations each) plus two code-signing CAs, all created in April 2025. One crumb of good news: no TLS certificate chaining to the six website intermediates had been logged to Certificate Transparency before Chrome's block, so none of them could have been trusted by default in Chrome or any browser that requires CT logging.
Emergency blocks across the ecosystem
Mozilla received the report at 20:06 UTC on October 17 and had its OneCRL blocklist rolled out to all standard Firefox users by 22:59 UTC — under three hours, with no browser update or restart required. On Tuesday it announced the incident publicly, shipped Firefox 158.0.1 and ESR releases for users with custom settings, and updated NSS to 3.131.1, which removes the eMudhra signing root from the trust store entirely. Apple followed on October 19 and Microsoft on October 20, while eMudhra revoked all eight intermediates.
The fix wave went beyond browsers. Go shipped emergency security releases (1.27.3 and 1.26.10) on its URGENT track — the track it reserves for threats to the ecosystem's integrity — plus fixes in Python's certifi bundle, Rust's webpki-roots, Electron and Homebrew's ca-certificates. Node.js and Composer's ca-bundle updates were still pending at the time of writing. The Golang trust store entry was assigned CVE-2026-111943.
What you should do
Users should update browsers and operating systems promptly. Developers should check the certificate bundles shipped with their applications rather than assuming the OS update covers every runtime, and administrators can use the incident disclosure site's test endpoints to assess remaining exposure. Revocation alone does not protect every client — some applications never receive browser blocklists or check revocation at all.
eMudhra, the Bengaluru-based certificate authority founded in 2008, has not yet publicly explained how the keys left its systems. It is not known when the keys leaked or whether anyone besides the reporting researcher holds them — and because certificate misuse can leave no forensic trace, previous abuse may never be discovered.
By Hamza Faisal
