Buffer Overflow in Viosock Driver for Windows Paravirtualized Drivers by Virtio-Win

CVE-2026-46655

What is CVE-2026-46655?

The Viosock driver in Virtio-Win is vulnerable to a buffer overflow due to inadequate bounds checking in the handling of IOCTL_SELECT requests. A low-privileged local process can exploit this vulnerability by submitting an attacker-controlled fd_count value, causing an overflow of the 32-bit sum which bypasses the FD_SETSIZE check. This leads to improper memory operations, allowing the attacker to write beyond the allocated kernel memory, resulting in potential privilege escalation within Windows guests utilizing this driver. The issue has been remedied in version mm320.

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