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Go blocks trust in eight eMudhra certificate intermediates

Go blocks trust in eight eMudhra certificate intermediates

Rule Changes

Go, Chrome, Firefox and Android block weak eMudhra intermediate keys

October 20th, 2026: Go 1.27.3 and 1.26.10 released

Overview

Updated Oct 21

Go has released versions 1.27.3 and 1.26.10 that refuse any TLS certificate chain built on one of eight compromised eMudhra intermediate keys. Researchers say the keys were weak enough that an attacker could forge a trusted certificate for any domain and impersonate the site.

Mozilla blocked the certificates in Firefox through OneCRL within three hours of the October 17 report, and Chrome and Android received the block through CRLSet and Google Play Services. eMudhra says the keys came from an April 2025 key generation ceremony and that the intermediates issued no end-entity certificates.

Why it matters

These weak keys let anyone mint a trusted certificate for any domain, so Go programs and major browsers all had to be patched.

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Key Indicators

8
Distrusted SPKI hashes
Keys Go rejects in any certificate chain, including chains a program trusts on its own.
16
eMudhra CA certificates affected
Intermediate CA certificates listed in the CCADB that share the eight blocked keys.
2
Go releases patched
Go 1.26.10 and 1.27.3 shipped on October 20; Go 1.28 will include the fix.
3
Hours to block in Firefox
Mozilla pushed the OneCRL block to standard Firefox installs by 22:59 UTC on October 17.

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People Involved

FV
Filippo Valsorda
Independent Go cryptography maintainer
Said the keys are compromised and the certificates revoked, and that blocking them in Go's code was the only option for now

Organizations Involved

eMudhra
eMudhra
Certificate Authority
Says eight intermediates from an April 2025 ceremony were compromised; root keys unaffected

Indian certificate authority operating under the emSign brand.
Go security team
Go security team
Programming language security group
Released Go 1.27.3 and 1.26.10 with the key block on October 20

The team that maintains security for the Go programming language.

Timeline

11 events Latest: October 20th, 2026 · 3 weeks ago Showing 8 of 11
Tap a bar to jump to that date

  1. Go 1.27.3 and 1.26.10 released

    Latest Release

    The patched releases reject any chain containing one of the eight keys, including when a program supplies its own set of trusted roots. There is no setting to turn the filter off.

  2. Firefox 158.0.1 and NSS 3.131.1 ship

    Release

    Mozilla released Firefox 158.0.1, ESR 115.43.1 and ESR 153.5.1 for users whose settings blocked the OneCRL update. NSS 3.131.1 drops a root certificate that signed the affected intermediates.

  3. eMudhra describes the April 2025 ceremony

    Statement

    eMudhra said the affected intermediates came from a key generation ceremony in April 2025, that its root CA keys were not affected, and that none of the intermediates issued end-entity certificates.

  4. Test certificates reveal the issue

    Discovery

    Test certificates from eMudhra intermediates appear in CT logs, including 'we-have-a-problem.com' domains.

  5. Go blocks eight eMudhra intermediates

    Security

    Go security team announces it will reject chains with eight distrusted eMudhra SPKIs (CVE-2026-111943).

  6. Fix merged and backported

    Release

    Fix merged to Go master and backported to the 1.26 and 1.27 branches; the patched releases shipped the following day.

  7. Chrome blocks the eight keys

    Security

    Chrome landed a CRLSet update that blocks the eight keys by public key hash, covering every certificate that shares them without a browser restart.

  8. Android and Googlebooks get the block

    Security

    Google sent an equivalent update through Google Play Services; Android users can also trigger it by restarting.

  9. CT logs block eMudhra certificates

    Security

    Two CT log operators block eMudhra-issued certificates, signaling suspected key compromise.

  10. Mozilla receives compromise report

    Discovery

    Mozilla was told that private keys for eight eMudhra intermediate certificates had been compromised and could be used to impersonate websites.

  11. Firefox blocks the certificates

    Security

    Mozilla pushed the OneCRL revocation to all Firefox users on standard settings in under three hours, without a browser update or restart.

Scenarios

1

Mozilla, Apple, and Google follow Go in distrusting eMudhra

Likely Resolves by Apr 19, 2027

Discussed by: Mozilla CA Certificate Policy group, CCADB

If the suspected private key compromise is confirmed, other trust stores will likely follow Go's lead. Mozilla's process for CA distrust involves public discussion and a vote by the Mozilla CA Certificate Policy group. Apple and Google typically act faster when a compromise is confirmed.

2

eMudhra reissues certificates and restores trust

Possible Resolves by Jan 19, 2027

Discussed by: eMudhra, affected customers

If the issue is contained to specific intermediates and eMudhra can demonstrate remediation, it may reissue certificates from unaffected intermediates. Affected customers would need to update their server configurations to restore TLS connections.

3

Investigation confirms private key compromise, full CA distrust

Uncertain Resolves by Apr 19, 2027

Discussed by: Security researchers, CT log operators

If the CT log blocking reflects a confirmed private key compromise, eMudhra's root CAs could face full distrust across the ecosystem. This would be the most severe outcome, similar to DigiNotar in 2011, and would force all eMudhra customers to migrate to a different CA.

4

Node.js ships a block for the eight eMudhra keys

Likely Resolves by End of 2026

Discussed by: Node.js project contributors

A draft change in Node.js would block the eight keys, matching what Go, Firefox and Chrome have done. Until it lands, Node.js programs that rely on their own verifier may still accept a forged chain.

Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

July-September 2011

DigiNotar compromise (2011)

Dutch certificate authority DigiNotar was compromised in 2011. Attackers issued fraudulent certificates for Google, Yahoo, Mozilla, and other major sites. The breach was discovered after a fraudulent Google certificate was found in the wild.

Then

All major browsers distrusted DigiNotar within weeks. The company went bankrupt.

Now

Established the playbook for CA compromise response: immediate distrust, forensic investigation, and CA shutdown.

Why this matters now

Shows what happens when a CA's private keys are compromised. The eMudhra situation may follow a similar path if the compromise is confirmed.

2017-2018

Symantec CA distrust (2017)

Google announced it would distrust Symantec's certificates after years of misissuance by Symantec and its subsidiaries. The distrust was phased in over 18 months, giving affected customers time to reissue.

Then

Symantec sold its certificate business to DigiCert.

Now

Established that even large CAs can face distrust for systemic misissuance.

Why this matters now

Shows the gradual process of CA distrust, in contrast to the rapid action Go took with eMudhra.

November-December 2022

TrustCor removal (2022)

Investigative reporting by The Record revealed that TrustCor's leadership had ties to a surveillance company. Mozilla and other trust stores removed TrustCor within weeks.

Then

TrustCor was removed from major trust stores.

Now

Established that CA trust requires not just technical security but also organizational integrity.

Why this matters now

Shows the trust store review process in action and how quickly distrust can spread across the ecosystem.

Sources

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GitHub (golang/go) LavX News Lobsters Hacker News World Programming Google Security Blog Mozilla Security Blog BleepingComputer Cloudflare Blog The Hacker News eMudhra Ubuntu Blog