An issue was discovered in the Linux kernel through 5.9.1, as used with Xen through 4.14.x. drivers/xen/events/events_base.c allows event-channel removal during the event-handling loop (a race condition). This can cause a use-after-free or NULL pointer dereference, as demonstrated by a dom0 crash via events for an in-reconfiguration paravirtualized device, aka CID-073d0552ead5.
https://github.com/torvalds/linux/commit/073d0552ead5bfc7a3a9c01de590e924f11b5dd2
https://xenbits.xen.org/xsa/advisory-331.html
https://security.gentoo.org/glsa/202011-06
https://lists.debian.org/debian-lts-announce/2020/12/msg00015.html
https://lists.debian.org/debian-lts-announce/2020/12/msg00027.html
Source: MITRE
Published: 2020-10-22
Updated: 2022-04-26
Type: CWE-362
Base Score: 4.7
Vector: AV:L/AC:M/Au:N/C:N/I:N/A:C
Impact Score: 6.9
Exploitability Score: 3.4
Severity: MEDIUM
Base Score: 4.7
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Impact Score: 3.6
Exploitability Score: 1
Severity: MEDIUM