The upnp_event_prepare function in upnpevents.c in MiniUPnP MiniUPnPd through 2.1 allows a remote attacker to leak information from the heap due to improper validation of an snprintf return value.
https://www.vdoo.com/blog/security-issues-discovered-in-miniupnp
https://usn.ubuntu.com/4542-1/
https://lists.debian.org/debian-lts-announce/2019/05/msg00045.html
https://github.com/miniupnp/miniupnp/commit/bec6ccec63cadc95655721bc0e1dd49dac759d94