Major Tech Companies Block eMudhra Certificates Due to Compromised Keys

Google, Mozilla, Apple, and the Go programming language project have blocked certificates signed with eight compromised certificate authority (CA) keys. This action responds to an incident that could allow attackers to impersonate legitimate websites or services.

The compromised keys were associated with intermediate certificates issued by the Indian CA eMudhra. Six of these keys were used to issue TLS certificates for websites, while the remaining two were designated for code signing.

Preventing Fraudulent Certificate Misuse

The blocks aim to prevent browsers and applications from trusting fraudulent digital certificates that attackers might issue using the compromised keys. This measure reduces the risk of website impersonation and potential interception of encrypted communications.

However, the protections do not automatically extend to all users and applications. Mozilla, Google, and Apple have implemented blocks through their respective certificate-revocation mechanisms. Applications built with Go must be rebuilt using patched versions to receive the fix, and other software may also require updates depending on their certificate trust management.

Uncertainty remains regarding whether attackers have already exploited the compromised keys to issue fraudulent certificates. Google stated that its Certificate Transparency protections would have prevented affected TLS certificates from being trusted by default in Chrome before the blocks were enacted.

Mozilla indicated that users with standard Firefox configurations received its block without needing to update or restart the browser. The Go project maintainers have urged users to upgrade immediately to patched Go versions 1.27.3 and 1.26.10.

eMudhra is an India-based company providing digital identity, electronic signature, and public key infrastructure (PKI) services. Its offerings include issuing digital certificates for website authentication, electronic document signing, digital identity verification, and securing online transactions.

Dennis Jackson, a member of Mozilla’s cryptography engineering team, noted that eMudhra has revoked the compromised intermediate certificates. He stated, “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.” He added that many other clients do not consume revocation information and require software updates to ensure they no longer trust the compromised intermediates.

Details of Compromise Remain Unclear

Currently, no details are available regarding how the eMudhra compromise occurred or when it took place. Jackson mentioned that Mozilla first learned of the compromise on October 17 from a researcher who identified themselves only as Wayne. The researcher demonstrated access to the private keys associated with all eight intermediate certificate authorities by using each key to create a digital signature on a message stating, “We have a problem here – Wayne.”

Mozilla completed the process of blocking the compromised certificates approximately three hours later. Jackson explained that Mozilla’s centralized list of revoked certificates, introduced in 2015, allows for delivering this protection without requiring users to update or restart Firefox.

Since then, Mozilla has been collaborating with eMudhra and other root programs to investigate the root cause, responsibly disclose the incident, and help protect the broader ecosystem. Jackson stated that Mozilla currently has no evidence of similar impacts on other CAs.

A member of Google Chrome’s Root Program Team reported receiving news of the compromise around the same time as Mozilla and addressed the issue in less than two hours. They stated, “Following the initial block, we evaluated all other CA certificates in the Chrome Root Store trust boundary and found no other instances of this failure mode.” The team is also working with Certificate Transparency log software maintainers and log operators to reject certificates chaining to these compromised intermediate CAs in the future.

Maintainers of the Go project did not identify eMudhra by name but noted plans to block trust in a small set of intermediate certificates due to unspecified operational security concerns.

For organizations assessing their exposure, the affected certificates include six TLS intermediates — EM DV TLS CA, EM OV TLS CA, and EM EV TLS CA, each with G3B and G3C variants — issued under emSign Root TLS CA – G3. The affected certificates also comprise two code-signing intermediates, EM OV CS CA – G3B and EM OV CS CA – G3C, issued under emSign Root CS CA – G3.

Compromises involving certificate authorities have repeatedly led browser makers to revoke trust in digital certificates. Notably, in 2011, a breach at Dutch CA DigiNotar resulted in the issuance of numerous fraudulent digital certificates. In 2017, Google, Mozilla, and others took issue with Symantec’s chronic mis-issuance of certificates, leading to the eventual sale of Symantec’s CA business to DigiCert.

Source: Dark Reading