# CVE-2025-40350: net/mlx5e: RX, Fix generating skb from non-linear xdp_buff for striding RQ

> A bug in the mlx5 network driver causes kernel warnings or crashes when XDP programs modify buffer layouts, leading to denial of service.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40350, DEBIAN-CVE-2025-40350, GHSA-xffx-64g2-mrvp, ROOT-OS-UBUNTU-2404-CVE-2025-40350, UBUNTU-CVE-2025-40350

## What is CVE-2025-40350?

CVE-2025-40350 is a critical vulnerability in Linux, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

net/mlx5e: RX, Fix generating skb from non-linear xdp_buff for striding RQ

XDP programs can change the layout of an xdp_buff through
bpf_xdp_adjust_tail() and bpf_xdp_adjust_head(). Therefore, the driver
cannot assume the size of the linear data area nor fragments. Fix the
bug in mlx5 by generating skb according to xdp_buff after XDP programs
run.

Currently, when handling multi-buf XDP, the mlx5 driver assumes the
layout of an xdp_buff to be unchanged. That is, the linear data area
continues to be empty and fragments remain the same. This may cause
the driver to generate erroneous skb or triggering a kernel
warning. When an XDP program added linear data through
bpf_xdp_adjust_head(), the linear data will be ignored as
mlx5e_build_linear_skb() builds an skb without linear data and then
pull data from fragments to fill the linear data area. When an XDP
program has shrunk the non-linear data through bpf_xdp_adjust_tail(),
the delta passed to __pskb_pull_tail() may exceed the actual nonlinear
data size and trigger the BUG_ON in it.

To fix the issue, first record the original number of fragments. If the
number of fragments changes after the XDP program runs, rewind the end
fragment pointer by the difference and recalculate the truesize. Then,
build the skb with the linear data area matching the xdp_buff. Finally,
only pull data in if there is non-linear data and fill the linear part
up to 256 bytes.

## Which versions are affected by CVE-2025-40350?


## How do I fix CVE-2025-40350?

Apply the vendor's patch.

## Is CVE-2025-40350 being exploited?

There is no known exploitation of CVE-2025-40350 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40350 and fix it if it is affected.

What it is: CVE-2025-40350 is a critical vulnerability in Linux, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-40350 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-2025-40350/ (Markdown: https://insights.sbomify.com/CVE-2025-40350/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40350
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40350
- OSV: https://osv.dev/vulnerability/CVE-2025-40350

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40350/
Summaries are generated and may contain mistakes; the official description above is the record.