CVE 2017-7493
Quick Emulator (Qemu) built with the VirtFS, host directory sharing via Plan 9 File System(9pfs) support, is vulnerable to an improper access control issue. It could occur while accessing virtfs metadata files in mapped-file security mode. A guest user could use this flaw to escalate their privileges inside guest.
See the 
CVE page on Mitre.org
for more details.
