EMudhra Intermediate CA Compromise

2026-10-20T13:58:33+00:00

The private keys of eight eMudhra intermediate CA certificates have been compromised. They chain to roots trusted by the Mozilla, Microsoft, Apple and Chrome root programs and by many downstream trust stores.

How do we know?

To demonstrate that the keys are compromised, the original reporter Wayne signed the following message with the private key of each of the eight intermediate CAs and reported it to the Root Program Teams on the 17th of October:

We have a problem here - Wayne

proof.zip contains the message, and for each intermediate the certificate, its public key and a signature on the message. To verify with OpenSSL:

openssl x509 -in EM-DV-TLS-CA-G3B.crt.pem -noout -pubkey | diff - EM-DV-TLS-CA-G3B.pub.pem
openssl dgst -sha384 -verify EM-DV-TLS-CA-G3B.pub.pem -signature EM-DV-TLS-CA-G3B.sig message.txt

What actions have been taken?

The root programs and many downstream trust stores have taken action to protect their users. The certificates have been blocked in Firefox and Chrome since the 17th of October, in Apple devices since the 19th and in Microsoft since the 20th.

The issue was responsibly disclosed to downstream trust stores on the 19th of October. Many have already released updates or are in the process of releasing updates.

What are the consequences?

An attacker with the private key of any of the compromised intermediate CAs could impersonate any website or service.

This has already been remediated by Mozilla, Microsoft, Apple, and Chrome for their users through their tools for distributing revocation information such as OneCRL, CRLite and CRLSets.

The CA has also revoked the compromised intermediate certificates. However, many other clients do not consume revocation information and require software updates to ensure they no longer trust the compromised intermediates.

Does your client still trust the compromised intermediates?

Intermediate CA	Chains to	Result

To check curl or other command-line clients, run:

curl https://dv-g3b-emudhra.we-have-a-problem.com/
curl https://dv-g3b-aaa-emudhra.we-have-a-problem.com/

A certificate error means the client does not trust the compromised intermediates.

To check a trust store offline, chains.zip contains the certificate chain served by each of the twelve hosts above in PEM format, with instructions for verifying them with OpenSSL.

What actions can users take?

Users should update their browsers and operating systems to the latest versions as soon as possible.

What about developer software and packages?

Software	Patched version
Ubuntu ca-certificates	20260816ubuntu0.22.04.1, 20260816ubuntu0.24.04.1, 20260816ubuntu0.26.04.1, 20260816ubuntu0.26.10.1
Go	1.27.3, 1.26.10
Electron	44.9.1, 43.8.1, 42.11.16
Python certifi	2026.10.19
Rust rustls-webpki	0.103.16
Rust webpki-roots / webpki-root-certs	1.0.10
Homebrew ca-certificates	2026-09-25_1
Node.js	pending
Composer ca-bundle	pending
NSS	3.131.1
uv	0.13.4

Add more at github.com/galadran/we-have-a-problem.com.

Are there workarounds for macOS curl?

macOS blocks the compromised intermediates, but the built-in /usr/bin/curl verifies certificates against /etc/ssl/cert.pem without checking revocation, and that file has not been updated. To remove the affected roots from it, run:

sudo cp /etc/ssl/cert.pem /etc/ssl/cert.pem.bak &&
awk '/^(###|===) /{skip=0}
  /^=== .*\/CN=(AAA Certificate Services|emSign ECC Root CA - G3)$/{skip=1}
  !skip' /etc/ssl/cert.pem.bak | sudo tee /etc/ssl/cert.pem > /dev/null

Are there workarounds for Linux?

Until a distribution ships an updated ca-certificates package, expert users can distrust the affected roots in the system trust store. This is NOT recommended for ordinary users.

On Debian and Ubuntu, run as root:

sed -i \
  -e 's|^mozilla/emSign_ECC_Root_CA_-_G3.crt|!&|' \
  -e 's|^mozilla/Comodo_AAA_Services_root.crt|!&|' \
  /etc/ca-certificates.conf && update-ca-certificates

On Alpine, run as root:

apk add ca-certificates &&
sed -i -e 's|^mozilla/emSign_ECC_Root_CA_-_G3.crt|!&|' \
  /etc/ca-certificates.conf && update-ca-certificates

On Fedora, RHEL, CentOS Stream, Rocky Linux, AlmaLinux and Amazon Linux 2023, run as root:

d=/etc/pki/ca-trust/source/blocklist; [ -d $d ] || d=/etc/pki/ca-trust/source/blacklist
trust extract --overwrite --format=pem-bundle \
  --filter='pkcs11:object=Comodo%20AAA%20Services%20root;type=cert' \
  $d/Comodo_AAA_Services_root.pem &&
trust extract --overwrite --format=pem-bundle \
  --filter='pkcs11:object=emSign%20ECC%20Root%20CA%20-%20G3;type=cert' \
  $d/emSign_ECC_Root_CA_-_G3.pem &&
update-ca-trust

On openSUSE and SLES, run as root:

d=/etc/pki/trust/blocklist; [ -d $d ] || d=/etc/pki/trust/blacklist
trust extract --format=pem-bundle \
  --filter='pkcs11:object=Comodo%20AAA%20Services%20root;type=cert' \
  $d/Comodo_AAA_Services_root.pem &&
trust extract --format=pem-bundle \
  --filter='pkcs11:object=emSign%20ECC%20Root%20CA%20-%20G3;type=cert' \
  $d/emSign_ECC_Root_CA_-_G3.pem &&
update-ca-certificates

On Arch Linux, run as root:

trust extract --format=pem-bundle \
  --filter='pkcs11:object=emSign%20ECC%20Root%20CA%20-%20G3;type=cert' \
  /etc/ca-certificates/trust-source/blocklist/emSign_ECC_Root_CA_-_G3.pem &&
update-ca-trust

On NixOS, add to your configuration:

security.pki.caCertificateBlacklist = [
  "Comodo AAA Services root"
  "emSign ECC Root CA - G3"
];

Are there workarounds for NetBSD?

On NetBSD 10 and later, run as root:

certctl untrust /usr/share/certs/mozilla/all/emSign_ECC_Root_CA_-_G3.pem &&
certctl untrust /usr/share/certs/mozilla/all/Comodo_AAA_Services_root.pem

What actions can trust store operators take?

Please see this thread in Mozilla's dev-security-policy forum.

Which intermediates were compromised?

impacted-intermediates.json lists the eight intermediates and their Sectigo cross-signs. roots.json lists the roots they chain to.

Site published by Dennis Jackson. The source is on GitHub and PRs are welcome.