# CVE-2025-40292: virtio-net: fix received length check in big packets

> A malicious host can trigger a NULL pointer dereference in the Linux kernel virtio-net driver, causing a denial of service.

- **Severity:** High 8.4 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Dec 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-40292, DEBIAN-CVE-2025-40292, GHSA-3mv7-84x4-8439, ROOT-OS-DEBIAN-12-CVE-2025-40292, ROOT-OS-DEBIAN-13-CVE-2025-40292, ROOT-OS-UBUNTU-2404-CVE-2025-40292, UBUNTU-CVE-2025-40292

## What is CVE-2025-40292?

CVE-2025-40292 is a high-severity vulnerability in Linux, published on 8 Dec 2025. 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:

virtio-net: fix received length check in big packets

Since commit 4959aebba8c0 ("virtio-net: use mtu size as buffer length
for big packets"), when guest gso is off, the allocated size for big
packets is not MAX_SKB_FRAGS * PAGE_SIZE anymore but depends on
negotiated MTU. The number of allocated frags for big packets is stored
in vi->big_packets_num_skbfrags.

Because the host announced buffer length can be malicious (e.g. the host
vhost_net driver's get_rx_bufs is modified to announce incorrect
length), we need a check in virtio_net receive path. Currently, the
check is not adapted to the new change which can lead to NULL page
pointer dereference in the below while loop when receiving length that
is larger than the allocated one.

This commit fixes the received length check corresponding to the new
change.

## Which versions are affected by CVE-2025-40292?


## How do I fix CVE-2025-40292?

Apply the vendor's patch.

## Is CVE-2025-40292 being exploited?

There is no known exploitation of CVE-2025-40292 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40292 and fix it if it is affected.

What it is: CVE-2025-40292 is a high-severity vulnerability in Linux, published on 8 Dec 2025. 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-2025-40292 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-2025-40292/ (Markdown: https://insights.sbomify.com/CVE-2025-40292/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40292
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40292
- OSV: https://osv.dev/vulnerability/CVE-2025-40292

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40292/
Summaries are generated and may contain mistakes; the official description above is the record.