A heap-based buffer overflow was found in QEMU through 5.0.0 in the SDHCI device emulation support. It could occur while doing a multi block SDMA transfer via the sdhci_sdma_transfer_multi_blocks() routine in hw/sd/sdhci.c. A guest user or process could use this flaw to crash the QEMU process on the host, resulting in a denial of service condition, or potentially execute arbitrary code with privileges of the QEMU process on the host.
https://security.netapp.com/advisory/ntap-20210312-0003/
https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg01175.html
https://lists.debian.org/debian-lts-announce/2021/04/msg00009.html