A flaw was found in qemu Media Transfer Protocol (MTP) before version 3.1.0. A path traversal in the in usb_mtp_write_data function in hw/usb/dev-mtp.c due to an improper filename sanitization. When the guest device is mounted in read-write mode, this allows to read/write arbitrary files which may lead do DoS scenario OR possibly lead to code execution on the host.
https://www.openwall.com/lists/oss-security/2018/12/06/1
https://usn.ubuntu.com/3923-1/