Addressing the unauthorized issuance of multiple TLS certificates for 1.1.1.1

Over the past few days Cloudflare has been notified through our vulnerability disclosure program and the certificate transparency mailing list that unauthorized certificates were issued by Fina CA for 1.1.1.1, one of the IP addresses used by our public DNS resolver service. From February 2024 to August 2025, Fina CA issued twelve certificates for 1.1.1.1 without our permission. We did not observe unauthorized issuance for any properties managed by Cloudflare other than 1.1.1.1.

We have no evidence that bad actors took advantage of this error. To impersonate Cloudflare's public DNS resolver 1.1.1.1, an attacker would not only require an unauthorized certificate and its corresponding private key, but attacked users would also need to trust the Fina CA. Furthermore, traffic between the client and 1.1.1.1 would have to be intercepted.

While this unauthorized issuance is an unacceptable lapse in security by Fina CA, we should have caught and responded to it earlier. After speaking with Fina CA, it appears that they issued these certificates for the purposes of internal testing. However, no CA should be issuing certificates for domains and IP addresses without checking control. At Continue reading

Cloudflare incident on September 17, 2024

On September 17, 2024, during routine maintenance, Cloudflare inadvertently stopped announcing fifteen IPv4 prefixes, affecting some Business plan websites for approximately one hour. During this time, IPv4 traffic for these customers would not have reached Cloudflare, and users attempting to connect to websites assigned addresses within those prefixes would have received errors. 

We’re very sorry for this outage. 

This outage was the result of an internal software error and not the result of an attack. In this blog post, we’re going to talk about what the failure was, why it occurred, and what we’re doing to make sure this doesn’t happen again.

Background

Cloudflare assembled a dedicated Addressing team in 2019 to simplify the ways that IP addresses are used across Cloudflare products and services. The team builds and maintains systems that help Cloudflare conserve and manage its own network resources. The Addressing team also manages periodic changes to the assignment of IP addresses across infrastructure and services at Cloudflare. In this case, our goal was to reduce the number of IPv4 addresses used for customer websites, allowing us to free up addresses for other purposes, like deploying infrastructure in new locations. Since IPv4 addresses are a finite Continue reading