On 10 January 2024 from 15:57 UTC to 16:45 UTC, we experienced an issue where clients received 4XX level errors while accessing the S3 buckets in the eu-south-1 (Milan) region.  

During an internal configuration change, a software bug caused the invalidation of TLS certificates used by internal servers to establish mutual TLS handshakes with load balancers. Consequently, the load balancers could not successfully connect to the internal servers, leading to 4XX errors returned to client requests. Wasabi’s Engineering and Operations teams identified the issue and manually reconfigured the TLS certificates to restore functionality. A fix was deployed to the eu-south-1 region to address the underlying bug and to prevent this problem from happening again.