The ahci_commit_buf function in ide/ahci.c in QEMU allows attackers to cause a denial of service (NULL dereference) when the command header 'ad->cur_cmd' is null.
https://security.netapp.com/advisory/ntap-20210727-0001/
https://security-tracker.debian.org/tracker/CVE-2019-12067
https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg01487.html
https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg01358.html