qmp_guest_file_read in qga/commands-posix.c and qga/commands-win32.c in qemu-ga (aka QEMU Guest Agent) in QEMU 2.12.50 has an integer overflow causing a g_malloc0() call to trigger a segmentation fault when trying to allocate a large memory chunk. The vulnerability can be exploited by sending a crafted QMP command (including guest-file-read with a large count value) to the agent via the listening socket.
https://www.exploit-db.com/exploits/44925/
https://www.debian.org/security/2019/dsa-4454
https://usn.ubuntu.com/3826-1/
https://seclists.org/bugtraq/2019/May/76
https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg03385.html
https://lists.debian.org/debian-lts-announce/2019/02/msg00041.html
https://gist.github.com/fakhrizulkifli/c7740d28efa07dafee66d4da5d857ef6