emSign Checker

Updated 22 Oct 2026 · Chrome removes the root on 27 Oct

Is your site affected by the eMudhra (emSign) certificate distrust?

Enter a domain to check whether its certificate chains to emSign ECC Root CA - G3 or one of the eight revoked eMudhra intermediates. Your browser also tests every key in the chain for the weakness behind this incident.

Works for any public HTTPS site. We connect on port 443 and read the certificate it presents.

Key facts

  • Eight eMudhra (emSign) intermediate CA certificates had private keys smaller than 256, so anyone could recover them from the public certificate in under a second.
  • Six were for website (TLS) certificates and two for code signing. All were created in a key ceremony on 30 April 2025.
  • eMudhra revoked all eight on 18 October 2026. Chrome, Firefox, Apple and Microsoft block them.
  • Mozilla removed trust in the emSign ECC Root CA - G3 root on 20 October 2026. Chrome removes it on 27 October 2026.
  • About 30,000 certificates must be replaced, about 97% of them issued through ACME. No misuse of the weak keys has been reported.

Last updated . Sources listed below.

Live findings from this checker

We publish totals from the checks run here once enough domains have been checked: how many use eMudhra certificates and how many are still on the distrusted root. Individual domains are never published.

What happened

Indian certificate authority eMudhra (brand emSign) created 24 intermediate CA keys during a key ceremony on 30 April 2025. A faulty script produced a second set of weak keys alongside the strong ones, and because the labels looked alike, staff used the weak ones for eight certificates. Those eight P-384 private keys were all numbers smaller than 256. One of them was literally the number 4.

That means anyone could recover the keys from the public certificates in under a second and, in principle, sign trusted certificates for any domain. Six of the intermediates were for website (TLS) certificates and two for code signing.

Timeline

  1. Weak intermediate keys generated during eMudhra's key ceremony.
  2. A researcher reports the problem to Apple, Google, Microsoft, Mozilla and eMudhra. Chrome blocks the six TLS intermediates via CRLSet; Firefox blocks all eight via OneCRL.
  3. eMudhra revokes the eight certificates.
  4. Sectigo revokes its cross-signs. Apple devices block the intermediates.
  5. Mozilla ships Firefox 158.0.1 and NSS 3.131.1, removing emSign ECC Root CA - G3. Microsoft platforms block the intermediates.
  6. Chrome drops emSign ECC Root CA - G3 (Chrome Root Store v43).

Who needs to act

  • Site owners on the emSign ECC G3 chain. eMudhra estimates about 30,000 certificates must move to its RSA chain (or to another CA). About 97% were issued through ACME, so most can be reissued automatically. See the fix guide.
  • Teams running servers, containers and apps. Non-browser clients use their own trust stores. Update NSS, your OS ca-certificates package, and libraries such as Rust webpki-roots (1.0.10 or later).
  • Everyone else. If your certificate is from another CA, you are not affected by this removal. Browsers already block the eight intermediates.

Frequently asked questions

Is my website affected by the eMudhra (emSign) incident?

Only if your certificate chains to the "emSign ECC Root CA - G3" root or one of the eight revoked intermediates. Enter your domain in the checker above to see your full chain. Certificates from other CAs, and eMudhra certificates on its RSA chain, are not affected by this root removal.

What happened with eMudhra certificates in October 2026?

The private keys of eight eMudhra intermediate CA certificates (six for TLS, two for code signing) were generated with values below 256, so anyone could recover them from the public certificate in under a second. They were reported on 17 October 2026, revoked by eMudhra on 18 October, and Mozilla then removed trust in the emSign ECC Root CA - G3 root.

When will Chrome stop trusting emSign ECC Root CA - G3?

Google has said Chrome will drop emSign ECC Root CA - G3 on 27 October 2026 (Chrome Root Store v43). Firefox removed it with Firefox 158.0.1 and NSS 3.131.1 on 20 October 2026. Sites still using that chain show security errors to visitors.

How many certificates need to be replaced?

eMudhra estimated about 30,000 certificates must move to its RSA chain, and said about 97% of them were issued through ACME, so most can be reissued automatically once the ACME client points at the new chain.

Were the weak keys used to attack anyone?

No misuse has been reported. Google said no website certificates chaining to the six TLS intermediates were logged in Certificate Transparency before the block, so forged certificates would not have worked in Chrome. It is not known whether anyone recovered the keys earlier, because the weak keys existed for about 17 months.

What is the weak-key test in this tool?

Your browser checks each public key in the chain for known weaknesses: EC private keys that are small numbers (the exact eMudhra flaw), RSA keys with small factors, RSA primes that are too close together (Fermat factoring) and short key sizes. It runs locally and only uses public data.

Does this tool see my private key?

No. A certificate contains only a public key. Never paste a private key anywhere, including here; the paste box rejects anything that is not a certificate.

Sources