An out-of-bounds write flaw was found in the UAS (USB Attached SCSI) device emulation of QEMU in versions prior to 6.2.0-rc0. The device uses the guest supplied stream number unchecked, which can lead to out-of-bounds access to the UASDevice->data3 and UASDevice->status3 fields. A malicious guest user could use this flaw to crash QEMU or potentially achieve code execution with the privileges of the QEMU process on the host.
Seems like this is just an OOB access: https://lists.nongnu.org/archive/html/qemu-devel/2021-08/msg03581.html
Not sure if it's made it into version control/any release yet.
https://lists.nongnu.org/archive/html/qemu-devel/2021-08/msg03588.html suggests it's not in 6.1