PuTTY before 0.73 might allow remote SSH-1 servers to cause a denial of service by accessing freed memory locations via an SSH1_MSG_DISCONNECT message.
lists.opensuse.org/opensuse-security-announce/2019-10/msg00020.html
lists.opensuse.org/opensuse-security-announce/2019-10/msg00021.html
lists.opensuse.org/opensuse-security-announce/2019-10/msg00030.html
lists.tartarus.org/pipermail/putty-announce/2019/000029.html
security.netapp.com/advisory/ntap-20191127-0003/