# CVE-2026-89804: drm/nouveau/dmem: fix mismatched DMA unmap size for large folios

> A mismatched DMA unmap size in the nouveau driver leaks IOMMU mappings for large folios, potentially causing resource exhaustion or instability.

- **Severity:** High 8.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-89804, GHSA-f67x-82w6-7jjx, UBUNTU-CVE-2026-89804

## What is CVE-2026-89804?

CVE-2026-89804 is a high-severity memory corruption vulnerability in Linux, published on 16 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:

drm/nouveau/dmem: fix mismatched DMA unmap size for large folios

Device-private THP migration maps migration buffers with page_size()
and records that length in dma_info->size.  For a compound folio
page_size() is PAGE_SIZE << order, but two teardown sites still pass a
literal PAGE_SIZE to dma_unmap_page():

  - nouveau_dmem_migrate_to_ram() on the success path, and
  - nouveau_dmem_migrate_copy_one() on the copy-error path.

For an order > 0 folio this unmaps less than was mapped, leaking the
remainder of the IOMMU/IOVA mapping.  The other unmap sites, in
nouveau_dmem_migrate_chunk() and nouveau_dmem_evict_chunk(), already
use the saved size; use it here too.

## Which versions are affected by CVE-2026-89804?


## How do I fix CVE-2026-89804?

Apply the vendor's patch.

## Is CVE-2026-89804 being exploited?

There is no known exploitation of CVE-2026-89804 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89804 and fix it if it is affected.

What it is: CVE-2026-89804 is a high-severity memory corruption vulnerability in Linux, published on 16 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-2026-89804 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-2026-89804/ (Markdown: https://insights.sbomify.com/CVE-2026-89804/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89804
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89804
- OSV: https://osv.dev/vulnerability/CVE-2026-89804

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89804/
Summaries are generated and may contain mistakes; the official description above is the record.