http://www.rfc-editor.org/rfc/rfc8270.txt
RFC 8270: Increase the Secure Shell Minimum Recommended Diffie-Hellman Modulus Size to 2048 Bits, L. Velvindron, M. Baushke2017-12-01T23:00:00-00:00The Diffie-Hellman (DH) Group Exchange for the Secure Shell (SSH) transport-layer protocol specifies that servers and clients should support groups with a minimum modulus group size of 1024 bits. Recent security research has shown that the minimum value of 1024 bits is insufficient to protect against state-sponsored actors and any organization with enough computing resources. This RFC updates RFC 4419, which allowed for DH moduli less than 2048 bits; now, 2048 bits is the minimum acceptable group size.