# CVE-2026-46655: virtio-win: Integer overflow causing a heap overflow in Viosock driver

> A local attacker can exploit an integer overflow in the Viosock driver to corrupt kernel memory and escalate privileges on Windows guests.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 18 Sep 2026
- **Updated:** 23 Sep 2026
- **Also known as:** GHSA-qrhp-4mhp-hjwh

## What is CVE-2026-46655?

CVE-2026-46655 is a high-severity vulnerability in virtio-win kvm-guest-drivers-windows, published on 18 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-46655?


## How do I fix CVE-2026-46655?

No fix has been published for CVE-2026-46655 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-46655 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46655 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46655 and fix it if it is affected.

What it is: CVE-2026-46655 is a high-severity vulnerability in virtio-win kvm-guest-drivers-windows, published on 18 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46655 exists.

Affected product: virtio-win kvm-guest-drivers-windows. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-46655/ (Markdown: https://insights.sbomify.com/CVE-2026-46655/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46655
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46655
- OSV: https://osv.dev/vulnerability/CVE-2026-46655

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46655/
Summaries are generated and may contain mistakes; the official description above is the record.