Weak eMudhra CA Keys Exposed for 17 Months; Browser Blocks Deployed
Summary
Eight eMudhra intermediate CA keys were recoverable from public certificates due to weak key generation. Major browsers blocked them, but clients with outdated trust stores may remain exposed; no malicious use was confirmed as of October 21, 2026.
Key points
- Eight eMudhra intermediates—six for TLS and two for code signing—used P-384 private-key values below 256, including one key equal to 4.
- The keys were created during an April 30, 2025 key ceremony and reported by an independent researcher on October 17, 2026.
- eMudhra blamed a flaw in its key-generation ceremony script and said its investigation and review of other ceremonies were ongoing.
- Chrome, Firefox, Apple, Microsoft and Sectigo blocked or revoked affected certificates; Mozilla removed the emSign ECC Root CA – G3, and Chrome's root removal was expected to reach all devices by October 27, 2026.
- Non-browser clients with bundled or outdated trust stores, and clients that skip revocation or Certificate Transparency checks, may still trust the compromised chain. Bun and FreeBSD fixes were pending as of October 21.
- No malicious use had been confirmed as of October 21, 2026. Google reported no affected TLS certificates in Certificate Transparency logs before the block, but misuse against clients not enforcing CT could not be ruled out.
- Teams are advised to update trust stores, rebuild Go binaries with fixed toolchains, test critical clients, replace affected certificates and review logs for possible misuse.
Article Details
- Event Type
- Certificate authority key compromise caused by eight eMudhra intermediate CA certificates containing trivially recoverable P-384 private keys.
- Impact
- The compromised TLS keys could be used to issue trusted certificates for arbitrary domains, while the code-signing keys could make malware appear to have a verified publisher signature on systems that skip revocation checks. No malicious use was confirmed as of October 21, 2026. Major browsers and trust stores blocked or revoked the affected certificates, but unpatched non-browser clients that skip revocation and Certificate Transparency checks remained at risk.
Indicators of compromise
| Type | Indicator | Context |
|---|---|---|
| DOMAIN | we-have-a-problem[.]com | The article identifies this domain as part of the public disclosure site's test hosts serving certificate chains through the compromised intermediates; it is a test indicator, not confirmed malicious infrastructure. |
| HOSTNAME | dv-g3b-aaa-emudhra[.]we-have-a-problem[.]com | Public disclosure-site test host serving a certificate chain through a compromised eMudhra intermediate cross-signed by Sectigo, used to test client trust. |
| HOSTNAME | dv-g3b-emudhra[.]we-have-a-problem[.]com | Public disclosure-site test host serving a certificate chain through a compromised eMudhra intermediate, used to test whether clients still trust it. |
CVE
CVE-2026-111943| CVE ID | None for the CA incident itself; downstream fixes tracked as CVE-2026-111943 (Go crypto/x509) and CVE-2026-113470 (Firefox OneCRL block list) |CVE-2026-113470| CVE ID | None for the CA incident itself; downstream fixes tracked as CVE-2026-111943 (Go crypto/x509) and CVE-2026-113470 (Firefox OneCRL block list) |
People
Dennis JacksonMozilla cryptography engineer who published a public disclosure site tracking affected software and patch status.Scott HelmeConducted tests in which curl, Python, and Node.js on Linux and macOS accepted a forged certificate issued under EM DV TLS CA – G3B.WayneIndependent researcher who discovered and reported the weak keys on October 17, 2026; Mozilla credits Wayne as the reporter of CVE-2026-113470.
Vendors
Apple- Browsers are covered: Chrome, Mozilla, Apple and Microsoft blocked the compromised certificates between October 17 and 20, 2026. Mozilla has also removed the emSign ECC Root CA – G3 root, and Chrome’s removal reacheseMudhraeMudhra CA Key Compromise: Weak Keys, Risks and FixesGoogleon October 17, 2026, while testing public certificate data, and reported it the same day to Apple, Google, Microsoft, Mozilla and eMudhra. As proof, they signed the message “We have a problem here” with each ofMicrosoft- Browsers are covered: Chrome, Mozilla, Apple and Microsoft blocked the compromised certificates between October 17 and 20, 2026. Mozilla has also removed the emSign ECC Root CA – G3 root, and Chrome’s removal reachesMozilla- Browsers are covered: Chrome, Mozilla, Apple and Microsoft blocked the compromised certificates between October 17 and 20, 2026. Mozilla has also removed the emSign ECC Root CA – G3 root, and Chrome’s removal reachesSectigo| Affected Products | Eight eMudhra intermediate CAs (six TLS, two code signing) and their Sectigo cross-signed copies; any client that trusts eMudhra’s G3 roots or Sectigo’s AAA Certificate Services without revocation
Products
Bun| Patch Available | Yes for browsers and most trust stores; Bun and FreeBSD pending as of October 21, 2026; Node.js fixed in 22.23.4, 24.22.1 and 26.12.1 |FreeBSD| Patch Available | Yes for browsers and most trust stores; Bun and FreeBSD pending as of October 21, 2026; Node.js fixed in 22.23.4, 24.22.1 and 26.12.1 |Go| CVE ID | None for the CA incident itself; downstream fixes tracked as CVE-2026-111943 (Go crypto/x509) and CVE-2026-113470 (Firefox OneCRL block list) |Google Chromefrom the public certificate. An independent researcher reported the weakness on October 17, 2026, and Chrome and Firefox blocked the intermediates within hours.Google Play Services| October 19, 2026 | Apple blocks the certificates; Sectigo revokes its cross-signed copies; Android update ships via Google Play Services |Microsoft Windowswould trust for any domain; the code-signing keys could lend malware a verified-publisher signature on Windows systems that skip revocation checks.Mozilla Firefoxpublic certificate. An independent researcher reported the weakness on October 17, 2026, and Chrome and Firefox blocked the intermediates within hours.Node.js| Patch Available | Yes for browsers and most trust stores; Bun and FreeBSD pending as of October 21, 2026; Node.js fixed in 22.23.4, 24.22.1 and 26.12.1 |NSS| Fixed In | Firefox 158.0.1, ESR 153.5.1 and ESR 115.43.1; NSS 3.131.1; Go 1.27.3 and 1.26.10; Python certifi 2026.10.19; updated Linux ca-certificates packages |Python certifi| Fixed In | Firefox 158.0.1, ESR 153.5.1 and ESR 115.43.1; NSS 3.131.1; Go 1.27.3 and 1.26.10; Python certifi 2026.10.19; updated Linux ca-certificates packages |Safari9. Are Chrome, Firefox and Safari Users Protected?