THE eMudhra CA key compromise concerns eight eMudhra intermediate CA certificates in the G3 hierarchy, whose private keys were recoverable from public certificates within milliseconds. All eight keys used P-384 values below 256, including a key that was simply the number 4. Six of the intermediates issue TLS certificates (DV, OV, EV) and two are code-signing CAs; Sectigo’s cross-signed copies also appear in those certificates.
Independent researcher Wayne disclosed the issue on 17 October 2026, and major browsers promptly blocked the compromised intermediates within hours, with Chrome’s and Firefox’s protections extending to users by 20 October and 27 October respectively.
The practical danger is that any entity possessing an intermediate CA private key can sign new certificates that chain to a trusted root, enabling spoofed TLS certificates for any domain or, for the code-signing keys, malware signed with a trusted publisher on systems that skip revocation checks. Chrome blocked the TLS intermediates via a CRLSet update on 17 October 2026; Mozilla implemented a OneCRL block the same day, and Apple and Android followed with platform-wide mitigations.
There is no confirmed exploitation as of 21 October 2026, but the keys were recoverable for about 17 months, and non-browser clients that do not perform revocation or CT checks remain exposed until trust stores are updated. Fixed in browsers and many trust stores are accompanied by downstream CVE identifiers: CVE-2026-111943 (Go crypto/x509) and CVE-2026-113470 (Firefox OneCRL block list).