Executive brief
A security vulnerability was found in QEMU, a widely used virtualization software that allows computers to run multiple operating systems simultaneously. A user with high privileges within a virtual machine could exploit a flaw in the virtual disk component to crash the host system or potentially interfere with other operations. This could lead to a denial of service, impacting the availability of the virtualized environment and the host server.
Technical details
A heap-based buffer overflow exists in QEMU's virtio-blk device during the handling of VIRTIO_BLK_T_SCSI_CMD requests. The vulnerability is caused by a failure to validate the size of input descriptors before writing the 4-byte virtio_scsi_inhdr.errors field. An attacker with high privileges in a guest VM can provide a descriptor pointing to an MMIO address with a length of only 1 byte, forcing QEMU to allocate a 1-byte heap bounce buffer. When QEMU writes the 4-byte error status, it performs an out-of-bounds write into the host's heap memory. This can result in a crash of the QEMU process (Denial of Service). A patch has been proposed to add the missing size check in hw/block/virtio-blk.c.
Affected products
- QEMU QEMU unspecified
Timeline
- 2026-05-26: patched: Upstream patch submitted to qemu-devel
- 2026-06-12: disclosed: CVE published and Red Hat advisory released