Technology1 min read

4 real? Tracking exploitation and patching of eMudhra’s weak keys

By · Published by Everything Blog

In short

Following the discovery of the trivial keys on October 19, 2026, Cloudflare deployed rapid updates across critical systems like its Pingora proxies to outright reject the compromised intermediate certificates. The provider used AI-assisted source code reviews to identify affected touchpoints and logged roughly 22,000 handshake attempts that used the leaked keys. Approximately 160 of these connections brandished unauthorized certificates for external entities, such as consumer IoT domains, bearing validity periods longer than two years.

Key points

  • An unreleased script configuration error caused eMudhra to completely withdraw from opera…: An unreleased script configuration error caused eMudhra to completely withdraw from operating as a public certificate authority.
  • Clients lacking Certificate Transparency enforcement remain vulnerable to domain spoofing…: Clients lacking Certificate Transparency enforcement remain vulnerable to domain spoofing from certificates generated using the exposed keys.
  • Lingering questions persist surrounding how external auditors, cross-signers, and monitor…: Lingering questions persist surrounding how external auditors, cross-signers, and monitoring failed to catch the weak key generation initially.

Sources checked by our analysis pipeline: 1

On October 19, 2026, we learned about eMudhra’s eight shockingly weak keys: where eMudhra was trusted to pick a 115-digit number for their virtual combination lock protecting the Internet, they picked the number 4. Not even four digits, just the number 4. The other seven keys were similarly weak: 56, 66, 115, 155, 156, 230 and 237.

The next day, we wrote a blog post on the immediate action we took to mitigate this leak, and what customers needed to do on their end to stay secure. Now, we are sharing a more in-depth follow up on the evidence we’ve seen of exploitation, and the progress seen on visitors patching their systems.

Let's start with the scale of the problem. A certificate authority (CA) with weak keys this serious is unprecedented, and the potential consequences are significant. While there have been plenty of compromised certification authorities in the past (such as DigiNotar, TÜRKTRUST, and TrustWave), access to their keys has always been contained to a degree; these incidents gave a limited set of attackers or organizations the ability to issue…

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