A flaw was found in the QXL display device emulation in QEMU. A double fetch of guest controlled values 'cursor->header.width' and 'cursor->header.height' can lead to the allocation of a small cursor object followed by a subsequent heap-based buffer overflow. A malicious privileged guest user could use this flaw to crash the QEMU process on the host or potentially execute arbitrary code within the context of the QEMU process. https://nvd.nist.gov/vuln/detail/CVE-2021-4207
