# CVE-2025-40159: xsk: Harden userspace-supplied xdp_desc validation

> Integer overflows in Linux kernel XSK descriptor validation allow attackers to cause undefined behavior or queue invalid frames, potentially leading to crashes or code execution.

- **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:** Yes
- **Published:** 12 Nov 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-40159, DEBIAN-CVE-2025-40159, GHSA-9mvj-23j7-q46q, ROOT-OS-UBUNTU-2404-CVE-2025-40159, UBUNTU-CVE-2025-40159

## What is CVE-2025-40159?

CVE-2025-40159 is a high-severity vulnerability in Linux, published on 12 Nov 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:

xsk: Harden userspace-supplied xdp_desc validation

Turned out certain clearly invalid values passed in xdp_desc from
userspace can pass xp_{,un}aligned_validate_desc() and then lead
to UBs or just invalid frames to be queued for xmit.

desc->len close to ``U32_MAX`` with a non-zero pool->tx_metadata_len
can cause positive integer overflow and wraparound, the same way low
enough desc->addr with a non-zero pool->tx_metadata_len can cause
negative integer overflow. Both scenarios can then pass the
validation successfully.
This doesn't happen with valid XSk applications, but can be used
to perform attacks.

Always promote desc->len to ``u64`` first to exclude positive
overflows of it. Use explicit check_{add,sub}_overflow() when
validating desc->addr (which is ``u64`` already).

bloat-o-meter reports a little growth of the code size:

add/remove: 0/0 grow/shrink: 2/1 up/down: 60/-16 (44)
Function                                     old     new   delta
xskq_cons_peek_desc                          299     330     +31
xsk_tx_peek_release_desc_batch               973    1002     +29
xsk_generic_xmit                            3148    3132     -16

but hopefully this doesn't hurt the performance much.

## Which versions are affected by CVE-2025-40159?


## How do I fix CVE-2025-40159?

Apply the vendor's patch.

## Is CVE-2025-40159 being exploited?

There is no known exploitation of CVE-2025-40159 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40159 and fix it if it is affected.

What it is: CVE-2025-40159 is a high-severity vulnerability in Linux, published on 12 Nov 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-2025-40159 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-2025-40159/ (Markdown: https://insights.sbomify.com/CVE-2025-40159/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40159
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40159
- OSV: https://osv.dev/vulnerability/CVE-2025-40159

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40159/
Summaries are generated and may contain mistakes; the official description above is the record.