pci_change_irq_level in hw/pci/pci.c in QEMU before 5.1.1 has a NULL pointer dereference because pci_get_bus() might not return a valid pointer.
http://www.openwall.com/lists/oss-security/2020/09/29/1
https://bugzilla.redhat.com/show_bug.cgi?id=1883178
https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg05294.html
https://ruhr-uni-bochum.sciebo.de/s/NNWP2GfwzYKeKwE?path=%2Flsi_nullptr1
Source: MITRE
Published: 2020-10-06
Updated: 2020-10-07
Type: CWE-476
Base Score: 2.1
Vector: AV:L/AC:L/Au:N/C:N/I:N/A:P
Impact Score: 2.9
Exploitability Score: 3.9
Severity: LOW
Base Score: 3.2
Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:L
Impact Score: 1.4
Exploitability Score: 1.5
Severity: LOW