Description
virtio-win provides Windows paravirtualized drivers for QEMU and KVM. From mm210 until mm320, the Viosock driver permits a low-privilege local process to submit an IOCTL_SELECT request with attacker-controlled VIRTIO_VSOCK_SELECT.Fdss[*].fd_count values that overflow the 32-bit sum used by VIOSockSelect for bounds checking. The wrapped sum can pass the FD_SETSIZE check even though an individual descriptor count is much larger than the expected limit. VIOSockSelectCopyFds then iterates using the unchecked count and writes beyond the allocated pPkt->Fds array in the NonPagedPool kernel heap. Successful exploitation can corrupt kernel memory and enable privilege escalation in a Windows guest running the driver. This issue is fixed in mm320.
References5
- github.com/virtio-win/kvm-guest-drivers-windows/commit/c6bef93d…
- github.com/virtio-win/kvm-guest-drivers-windows/pull/1568
- github.com/virtio-win/kvm-guest-drivers-windows/releases/tag/mm…
- github.com/virtio-win/kvm-guest-drivers-windows/security/adviso…
- github.com/virtio-win/kvm-guest-drivers-windows/security/adviso…
Metrics
- CVSS 3.1
-
7.8
HIGH
Score source: CNA
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 0% percentile: 7 · as of 8 November 2026
- CWE
- CWE-122CWE-190
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.