PuTTY is vulnerable to buffer overflows. There is triggerable buffer overflow in any kind of server-to-client forwarding.
lists.opensuse.org/opensuse-security-announce/2019-04/msg00004.html
lists.opensuse.org/opensuse-security-announce/2019-04/msg00020.html
lists.fedoraproject.org/archives/list/[email protected]/message/36LWQ3NPFIV7DC7TC4KFPRYRH2OR7SZ2/
lists.fedoraproject.org/archives/list/[email protected]/message/LDO3F267P347E6U2IILFCYW7JPTLCCES/
seclists.org/bugtraq/2019/Apr/6
security.netapp.com/advisory/ntap-20190404-0001/
www.chiark.greenend.org.uk/~sgtatham/putty/changes.html
www.debian.org/security/2019/dsa-4423