QEMU: missing iov bounds check in the virtio-snd input callback gives a guest a heap out-of-bounds write

Impact

The virtio-snd input callback writes captured audio into the guest-supplied iov without checking that it fits, producing a heap out-of-bounds write inside the QEMU process on the host. QEMU runs with access to every device assigned to that guest, so a successful write is a step toward host-side code execution and, from there, to other tenants on the same hypervisor and to the passthrough or vGPU state of the accelerators attached to it. Scope is narrow in practice: only guests configured with an emulated virtio sound device are affected, which is uncommon on GPU compute machine types, and Red Hat rates attack complexity high. This is an incomplete fix for CVE-2024-7730 - hosts patched only for that CVE are still exposed.

Who can reach it

A tenant with code execution inside a guest whose machine type includes a virtio-snd device; no host credentials required, and the record scores it local (AV:L) with high attack complexity. Guests with no emulated sound device do not reach the affected code.

What to do

Apply the QEMU update from your distribution - Red Hat has published a VEX record and CVE page for RHEL 6-10 and OpenShift Container Platform 4, but the record given here names no fixed package version, so take the version from the errata rather than assuming one. A patched binary only takes effect on a fresh QEMU process, so each running guest must be live-migrated or restarted; on a GPU host with passthrough devices that means draining the node. Interim mitigation: remove virtio-snd from GPU guest machine types, where it has no purpose.

References

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