OpenSSH is a complete SSH protocol implementation that includes SFTP client and server support.
OpenSSH, when built with “xmss” USE flag enabled, has a pre-authentication integer overflow if a client or server is configured to use a crafted XMSS key.
NOTE: This USE flag is disabled by default!
A remote attacker could connect to a vulnerable OpenSSH server using a special crafted XMSS key possibly resulting in execution of arbitrary code with the privileges of the process or a Denial of Service condition.
Disable XMSS key type.
All OpenSSH users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose
">=net-misc/openssh/openssh-8.0_p1-r4"