# CVE-2025-40172: accel/qaic: Treat remaining == 0 as error in find_and_map_user_pages()

> A local attacker can trigger a general protection fault and crash the system by sending a zero-length DMA transfer request to the QAIC accelerator driver.

- **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:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40172, DEBIAN-CVE-2025-40172, GHSA-q638-pmrf-wwcc, ROOT-OS-DEBIAN-13-CVE-2025-40172, ROOT-OS-UBUNTU-2404-CVE-2025-40172, UBUNTU-CVE-2025-40172

## What is CVE-2025-40172?

CVE-2025-40172 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:

accel/qaic: Treat remaining == 0 as error in find_and_map_user_pages()

Currently, if find_and_map_user_pages() takes a DMA xfer request from the
user with a length field set to 0, or in a rare case, the host receives
QAIC_TRANS_DMA_XFER_CONT from the device where resources->xferred_dma_size
is equal to the requested transaction size, the function will return 0
before allocating an sgt or setting the fields of the dma_xfer struct.
In that case, encode_addr_size_pairs() will try to access the sgt which
will lead to a general protection fault.

Return an EINVAL in case the user provides a zero-sized ALP, or the device
requests continuation after all of the bytes have been transferred.

## Which versions are affected by CVE-2025-40172?


## How do I fix CVE-2025-40172?

Apply the vendor's patch.

## Is CVE-2025-40172 being exploited?

There is no known exploitation of CVE-2025-40172 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40172 and fix it if it is affected.

What it is: CVE-2025-40172 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-2025-40172 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-2025-40172/ (Markdown: https://insights.sbomify.com/CVE-2025-40172/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40172
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40172
- OSV: https://osv.dev/vulnerability/CVE-2025-40172

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40172/
Summaries are generated and may contain mistakes; the official description above is the record.