Browsers block eMudhra intermediate CAs with recoverable private keys
Original title: Browsers Block eMudhra Intermediate CAs Over Recoverable Private Keys
Eight April 2025 intermediates used near all-zero keys; browsers blocked them between October 17 and October 20.
Private keys for eight intermediate certificates issued by Indian CA eMudhra were generated with weak entropy and can be recovered, Google says, letting anyone forge trusted HTTPS certificates for clients that still trust those CAs. Mozilla and Google blocked them in Firefox and Chrome on October 17; Apple and Microsoft followed on October 19 and October 20. eMudhra revoked the certificates and blamed a key-ceremony script that created a second, weaker key pair. No Certificate Transparency evidence of malicious use before revocation is reported.
Unconfirmed: CT logs show no malicious use before revocation, but clients that do not enforce CT may still have been impersonated.
- Keys are effectively all zeroes except the last byte and recover via baby-step giant-step.
- Mozilla's Dennis Jackson published a client trust-check tool; several people recovered the keys.
- Sectigo took revocation steps and Cloudflare patched its services.
- eMudhra says most issuers never went into production except one.
- Some clients may need software updates to drop trust in the intermediates.
Impact: Forge trusted HTTPS certificates and impersonate any website
| Product | Affected |
|---|---|
| eMudhra intermediate certificates | eight intermediates issued in April 2025 |
- 1.Update clients so the revoked eMudhra intermediates are no longer trusted.
- 2.Use Mozilla's published tool to check whether a client still trusts them.
- Organizations
- SectigoCloudflare
- Countries
- India
From the original article
2 min read at securityweek.com
The private keys associated with eight certificates were compromised, and root programs and trust stores are blocking them. The post Browsers Block eMudhra Intermediate CAs Over Recoverable Private Keys appeared first on SecurityWeek.
By Ionut Arghire · securityweek.com
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