eMudhra revokes eight intermediates with weak keys; Go distrusts them

eMudhra revokes eight intermediates with weak keys; Go distrusts them

19 October 2026: Eight issuing certificate authorities run by the Indian CA eMudhra under its emSign G3 roots were revoked on 18 October with the reason "cACompromise", and Go 1.27.3 and 1.26.10, released on 19 October as CVE-2026-111943, stop any certificate chain that passes through them. Sites and code-signing customers holding certificates from those CAs need new ones from a different issuer.

Update, 28 October 2026: Microsoft released an out-of-band Windows 11 update, KB5134133, on 26 October for devices that do not receive current certificate trust list updates, such as machines in disconnected networks, devices that cannot reach Microsoft's certificate-update service and devices where automatic trust list updates are disabled. It carries an updated trusted root certificate payload and points to Microsoft's response to the compromised eMudhra keys. Connected Windows devices get the change through the normal trust list service; it is the offline and locked-down ones that need this update. Microsoft notes that hotpatch-enrolled devices that install it will receive no further hotpatches until after the January 2027 baseline update.

Not yet independently verified. eMudhra's own statement says the eight intermediates had weak keys from a script error and that its infrastructure was not compromised. The root cause analysis it promised through CCADB and KPMG's independent review are not yet published. We will update this when it can be confirmed, and remove this note.

Update, 9 November 2026: eMudhra has now said what happened. Its statement of 26 October says a researcher reported that the private keys of the eight emSign G3 intermediates could be recovered, that "a script error resulted in issuing CA's with weak keys", and that the intermediates were revoked within 14 hours of confirmation. It says they had issued no publicly trusted end-entity certificates and that its infrastructure and customer data were not compromised. CCADB's revocation reason remains cACompromise. eMudhra says about 30,800 certificates under the affected G3 hierarchies belong to a client ecosystem in the United States, now moved to its G1 root, and it appointed KPMG as independent reviewer on 30 October. It is winding down publicly trusted TLS, and gives the phase-out dates for G1 certificates as 16 November for new issuance trusted by Chrome and Firefox, and 30 November for removal by Apple, which affects every G1 certificate whenever it was issued.

Which certificates are affected

The Common CA Database lists the eight as revoked by eMudhra Technologies on 18 October, all valid from 30 April 2025:

Issuing CA	Root	Subject organisation
EM DV TLS CA - G3B, EM EV TLS CA - G3B, EM OV TLS CA - G3B	emSign Root TLS CA - G3	eMudhra BV (Netherlands)
EM DV TLS CA - G3C, EM EV TLS CA - G3C, EM OV TLS CA - G3C	emSign Root TLS CA - G3	eMudhra Inc (United States)
EM OV CS CA - G3B, EM OV CS CA - G3C	emSign Root CS CA - G3	eMudhra BV and eMudhra Inc

The same eight subjects also had cross-signed copies under Sectigo's AAA Certificate Services root, and Sectigo revoked all eight of those on 19 October, also for CA compromise. The six TLS CAs cover domain, organisation and extended validation certificates; the two CS CAs issue code-signing certificates. Older G2A and G3A issuing CAs were retired for cessation of operation in May 2025 and are not part of this.

What the Go release changes

The Go team's issue says it is "blocking trust in a small set of intermediate certificates due to specific security concerns around their operation", that Verify now filters out chains containing them, and that it "highly" recommends upgrading at once. It was handled on Go's urgent security track. The fix shipped as go1.27.3 and go1.26.10, which the release history describes only as security fixes to crypto/x509. Go 1.25 and older get no fix, because only the two newest major versions are supported.

Revocation alone does not stop every client, since many never check revocation lists for intermediates. That is why Go, which ships its own verifier, hard-codes the distrust, and why browsers and operating system root programmes are likely to follow with their own blocklists.

Finding emSign certificates in your estate

• Search certificate inventories and Certificate Transparency logs for the eight issuer names above, including code-signing certificates used on software releases.
• Rebuild Go services on 1.27.3 or 1.26.10; until then a Go client will still accept these chains.
• Expect a TLS failure, not a warning, from any Go-based tool that meets a server still presenting one of these chains.

Company profile on TrustList: eMudhra

Update, 22 October 2026: Docker Desktop 4.96.1 (21 October) and 4.96.2 (22 October) remove trust for certificates issued by the compromised eMudhra intermediates. Docker warns that an attacker with network access could have used them to intercept TLS connections made by non-browser clients such as the Docker CLI and daemon, and says the fix is reaching its components in batches over the next patch releases. The Node.js security releases of 21 October make the same change to Node's bundled certificate store.

Sources

• Go issue 82345: crypto/x509 mitigation for security concerns with a specific Certificate Authority (CVE-2026-111943), 19 October 2026
• Go: release history, go1.27.3 and go1.26.10, 19 October 2026
• CCADB: public intermediate certificates revoked (read 2026-10-20), 20 October 2026
• Docker: Docker Desktop release notes, 4.96.1 and 4.96.2 - 22 October 2026
• Mozilla Foundation Security Advisory 2026-111, 20 October 2026
• Microsoft Support: October 26, 2026, KB5134133 (OS Builds 26300.9725, 26200.9725 and 26100.9725) Out-of-band, 26 October 2026
• eMudhra: Certificate security incident statement and updates, first published 20 October 2026, last updated 5 November 2026