# CVE-2026-46209: drm/gem: Fix inconsistent plane dimension calculation in drm_gem_fb_init_with_funcs()

> An integer overflow in Linux kernel DRM allows out-of-bounds memory access, potentially leading to code execution or data disclosure.

- **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:** 28 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-88985, BELL-CVE-2026-46209, DEBIAN-CVE-2026-46209, GHSA-f8g6-g8cv-582v, ROOT-OS-DEBIAN-11-CVE-2026-46209, ROOT-OS-DEBIAN-12-CVE-2026-46209, ROOT-OS-UBUNTU-2204-CVE-2026-46209, ROOT-OS-UBUNTU-2404-CVE-2026-46209, UBUNTU-CVE-2026-46209

## What is CVE-2026-46209?

CVE-2026-46209 is a high-severity vulnerability in Linux kernel, published on 28 May 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/gem: Fix inconsistent plane dimension calculation in drm_gem_fb_init_with_funcs()

drm_gem_fb_init_with_funcs() computes sub-sampled plane dimensions
using plain integer division:

  unsigned int width  = mode_cmd->width  / (i ? info->hsub : 1);
  unsigned int height = mode_cmd->height / (i ? info->vsub : 1);

However, the ioctl-level framebuffer_check() in drm_framebuffer.c uses
drm_format_info_plane_width/height() which round up dimensions via
DIV_ROUND_UP(). This inconsistency corrupts the subsequent GEM object
size check for certain pixel format and dimension combinations.

For example, with NV12 (vsub=2) and a 1-pixel-tall framebuffer the
GEM size validation path sees height=0 instead of height=1. The
expression (height - 1) then wraps to UINT_MAX as an unsigned int,
causing min_size to overflow and wrap back to a small value. A tiny
GEM object therefore passes the size guard, yet when the GPU accesses
the chroma plane it will read or write memory beyond the object's
bounds.

Fix by replacing the open-coded divisions with drm_format_info_plane_width()
and drm_format_info_plane_height(), which use DIV_ROUND_UP() and match
the calculation already used in framebuffer_check().

Weakness: CWE-787 (Out-of-bounds Write), CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-46209?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-46209?

Apply the vendor's patch.

## Is CVE-2026-46209 being exploited?

There is no known exploitation of CVE-2026-46209 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46209 and fix it if it is affected.

What it is: CVE-2026-46209 is a high-severity vulnerability in Linux kernel, published on 28 May 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-2026-46209 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-46209/ (Markdown: https://insights.sbomify.com/CVE-2026-46209/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46209
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46209
- OSV: https://osv.dev/vulnerability/CVE-2026-46209

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46209/
Summaries are generated and may contain mistakes; the official description above is the record.