US Department of Energy has confirmed that the hacking group behind the SolarWinds compromise also hacked the networks of the US nuclear weapons agency. The group behind this compromise campaign is suspected to be the Russian state-sponsored APT29 (aka Cozy Bear) CISA has also issued an Emergency Directive asking federal civilian agencies to immediately disconnect or shut down affected networks. The hackers have mainly focused their efforts at FERC according to the DOE officials, but they did not provide more details on the incident.
Source: https://www.bleepingcomputer.com/news/security/solarwinds-hackers-breach-us-nuclear-weapons-agency/