CVE 2021-26934
An issue was discovered in the Linux kernel 4.18 through 5.10.16, as used by Xen. The backend allocation (aka be-alloc) mode of the drm_xen_front drivers was not meant to be a supported configuration, but this wasn't stated accordingly in its support status entry.
See the 
CVE page on Mitre.org
for more details.
