Customers of Bitbucket attempting to use our SSH based service between roughly 12:11 PM to 12:59 PM UTC on February 10th may have experienced failures with the error message "Permission denied (publickey). fatal: Could not read from remote repository." Only a small percentage of overall customers would have experienced this problem.
This was caused by one of our application servers responsible for our SSH service misbehaving. We have identified improvements to our load balancers that will prevent this situation from happening in the future.