Issue with TLS certificates using Lets Encrypt CA

This incident has been resolved.

Cloudflare has identified an issue affecting a subset of Let's Encrypt certificates, in which unsupported CA bundling may result in TLS connectivity issues for some visitors. Customers requiring immediate resolution may order a replacement certificate; re-issuance from the same Certificate Authority will resolve the issue. Customer action is not required for a permanent fix — Cloudflare engineering is rebuilding all impacted certificate chains, and affected certificates will be automatically restored to a valid state.