A flaw was found in the QEMU virtio-fs shared file system daemon (virtiofsd) implementation. This flaw is strictly related to CVE-2018-13405. A local guest user can create files in the directories shared by virtio-fs with unintended group ownership in a scenario where a directory is SGID to a certain group and is writable by a user who is not a member of the group. This could allow a malicious unprivileged user inside the guest to gain access to resources accessible to the root group, potentially escalating their privileges within the guest. A malicious local user in the host might also leverage this unexpected executable file created by the guest to escalate their privileges on the host system.
Exploitability
AV:LAC:LPR:LUI:NScope
S:UImpact
C:HI:HA:H7.8/CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HOther