tcp_emu in tcp_subr.c in libslirp 4.1.0, as used in QEMU 4.2.0, mismanages memory, as demonstrated by IRC DCC commands in EMU_IRC. This can cause a heap-based buffer overflow or other out-of-bounds access which can lead to a DoS or potential execute arbitrary code.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:LI:LA:L5.6/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L