CircleCI User Key uses RSA with SHA1, which GitHub has deprecated

Hi all,

Thank you all for letting us know about the problem. We are tracking this internally and will provide an update when we have new information.

A current workaround we have is switching to a docker image that has a newer version of OpenSSH installed or using the latest version of our machine image.
We have confirmed that this resolve the issue for several users.

I hope that this helps, and please wait for further updates.

If you need further assistance please send us a ticket.

some quote from ssh-troubleshooting: Improving Git protocol security on GitHub - The GitHub Blog

Clients relying on older SSH implementations will need to be updated. (The standard Git client uses your operating system’s SSH implementation on Linux and macOS.) Common examples include:

  • OpenSSH before version 7.2
  • PuTTY before 0.75