# CVE-2026-97994: vhost/vdpa: reject VRING_NUM larger than device max

> A local attacker with access to vhost-vdpa devices can trigger an out-of-bounds read by setting an invalid queue size, potentially causing a kernel crash or information leak.

- **Severity:** Not scored
- **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:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104217, BELL-CVE-2026-97994, DEBIAN-CVE-2026-97994, GHSA-h9m6-p5f9-c339, UBUNTU-CVE-2026-97994

## What is CVE-2026-97994?

CVE-2026-97994 is a memory corruption vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

vhost/vdpa: reject VRING_NUM larger than device max

vhost_vring_set_num() accepts any non-zero power-of-two queue size that
fits in 16 bits. vhost-vdpa then passes that value to set_vq_num()
without comparing it with get_vq_num_max().

A process with access to /dev/vhost-vdpa-* can therefore configure a
queue larger than the device advertises. With vdpa_sim, the worker can
walk descriptors beyond the mapped descriptor ring. KASAN reports a
16-byte out-of-bounds read, corresponding to one vring_desc, in the
vringh IOTLB path:

  BUG: KASAN: out-of-bounds in _copy_from_iter
  Read of size 16
  copy_from_iotlb
  copydesc_iotlb
  vringh_getdesc_iotlb
  vdpasim_net_work

Cache get_vq_num_max() immediately after reset. Some backends derive
it from writable queue-size state, so querying it after SET_NUM may
return the current size instead of the device capability. Invalidate
the cached value before reset so a failed reset leaves SET_NUM
disabled.

For VHOST_SET_VRING_NUM, copy the complete vring state once and use
the same index and size for validation, vq->num, and set_vq_num().
This ensures that validation and use operate on the same copied values.

## Which versions are affected by CVE-2026-97994?


## How do I fix CVE-2026-97994?

Apply the vendor's patch.

## Is CVE-2026-97994 being exploited?

There is no known exploitation of CVE-2026-97994 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97994 and fix it if it is affected.

What it is: CVE-2026-97994 is a memory corruption vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-97994 in the wild and no public exploit code.

Affected product: Linux. 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-2026-97994/ (Markdown: https://insights.sbomify.com/CVE-2026-97994/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97994
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97994
- OSV: https://osv.dev/vulnerability/CVE-2026-97994

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97994/
Summaries are generated and may contain mistakes; the official description above is the record.