The eMudhra CA Compromise: Is Your Certificate Affected? Check in One Click

On October 17, 2026, a researcher reported that the private keys of eight eMudhra intermediate certificate authorities could be recovered. Not stolen, not leaked: recovered, from the certificates themselves, because of weak key generation. Several other people reproduced it independently. Within hours Chrome and Firefox blocked all eight. Apple and Microsoft followed. eMudhra revoked them. And then the browser root programs started pulling the roots above them.

If your certificate was issued by eMudhra or its emSign brand, this post tells you what is happening, when it bites, and how to check in one click. If you have no idea who issued your certificate, that is exactly what the check is for.

Check now

Run your domain through the certificate chain checker or the security scanner. If the chain touches a compromised eMudhra CA, the removed root, or any other eMudhra issuer, you get a red CA Alert with the level and the fix. Want to see what it looks like first? Scan the live test host that serves one of the compromised certificates.

Free, no account. Works on any public hostname.

What Happened, in Order

Oct 17

Report to the root programs: eight eMudhra intermediate CA keys are recoverable. Six issue TLS certificates, two issue code-signing certificates. Chrome and Firefox block them the same day.

Oct 18

eMudhra revokes the intermediates, reason: CA compromise.

Oct 19–22

Microsoft and Apple ship blocks. Mozilla removes the root that signed them, emSign ECC Root CA - G3, from Firefox.

Oct 27

Chrome removes the same root from the Chrome Root Store. Every certificate under it stops working in Chrome, compromised or not.

Open

Chrome is reviewing whether eMudhra’s remaining roots stay in the store at all. eMudhra estimates around 30,000 customer certificates need replacing.

Why This Is Worse Than a Normal Revocation

A leaked key is bad. A recoverable key is worse, because nobody has to leak it. Anyone who worked out the weakness could have minted a valid certificate for any domain on the internet, signed by a CA that every browser trusted, from April 2025 when these intermediates were created until the blocks landed. eMudhra says it has no evidence that happened. Nobody can prove it did not.

Two details make the cleanup messy. First, each of the eight intermediates exists twice: once signed by an emSign root, and once cross-signed by Sectigo’s old AAA Certificate Services root. Same key, two certificates, so a block has to catch both. Second, browsers update their block lists in hours, but the trust store baked into your API client, your Java runtime, your Docker image, or your IoT fleet does not. Those keep trusting the compromised CAs until someone ships a package update and you install it.

Who Is Affected

Certificates issued by one of the eight compromised intermediates. Already revoked and blocked. Visitors see errors today. Replace immediately.
Any certificate under emSign ECC Root CA - G3. Not compromised, but the root is gone from Firefox and leaves Chrome on October 27. Replace before then.
Anything else from eMudhra or emSign. Works today. The Chrome review of the remaining roots is open, so plan the move at renewal, or sooner if there is further news.

Those three cases are exactly the three levels the check reports: CA Revoked, CA Distrusted, and CA Review. The compromised intermediates are matched by their public key, not their name, so both the emSign-signed and the Sectigo cross-signed copies are caught. Sectigo’s AAA root itself is deliberately not flagged: thousands of unrelated certificates chain through it and are fine.

How to Check

Open the certificate chain checker and enter your hostname. It pulls the chain your server actually sends and walks every certificate in it.
Look at the verdict. A clean chain says TRUSTED. An affected one says CA REVOKED or CA DISTRUSTED, with the exact intermediate or root that triggered it.
Have a certificate file but no live server? Paste it into the certificate decoder. It flags the certificate by its key, or its issuer by name.
The full security scan includes the same check in its SSL row, alongside everything else.

What to Do If You Are Hit

Get a certificate from a different CA. Not a reissue from eMudhra. The whole hierarchy is under review, and a reissue under the same root just moves the deadline.
Check the things that are not browsers. Internal services, API integrations, mobile apps with pinned chains, mail servers, VPN appliances. Each one has its own trust store and its own update cadence.
Update trust stores on your own servers. Linux distributions, the curl CA bundle, and language runtimes shipped fixes starting October 20. Install them, or your servers keep trusting the compromised CAs when they talk to other systems.
Rescan after you swap. The chain checker should go back to TRUSTED.

Not Hit Today? Watch for the Next One

The check is not a one-off. Every domain in an InternetSecure account is scanned daily, and the moment a chain starts touching a flagged CA, the change lands in your alert digest with the level and the fix. When the Chrome review of eMudhra’s remaining roots concludes, or the next CA has a bad week, you will know before your visitors do.

Create a free account to monitor your domains, or run a one-off check at internetsecure.org/certdeepdive.