CVE-2018-16872

A flaw was found in qemu Media Transfer Protocol (MTP). The code opening files in usbmtpgetobject and usbmtpgetpartialobject and directories in usbmtpobjectreaddir doesn't consider that the underlying filesystem may have changed since the time lstat(2) was called in usbmtpobject_alloc, a classical TOCTTOU problem. An attacker with write access to the host filesystem shared with a guest can use this property to navigate the host filesystem in the context of the QEMU process and read any file the QEMU process has access to. Access to the filesystem may be local or via a network share protocol such as CIFS.