# CVE-2026-64524: drm/hyperv: validate resolution_count and fix WIN8 fallback

> A missing bounds check in the Hyper-V DRM driver allows an out-of-bounds read via crafted resolution counts, potentially causing a denial of service.

- **Severity:** High 7.7 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Jul 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-64524, DEBIAN-CVE-2026-64524, GHSA-2rhv-cg46-xrx8, ROOT-OS-UBUNTU-2204-CVE-2026-64524, UBUNTU-CVE-2026-64524

## What is CVE-2026-64524?

CVE-2026-64524 is a high-severity vulnerability in Linux, published on 25 Jul 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/hyperv: validate resolution_count and fix WIN8 fallback

A SYNTHVID_RESOLUTION_RESPONSE with resolution_count > 64 walks past
the supported_resolution[SYNTHVID_MAX_RESOLUTION_COUNT] array in the
parse loop. Bound resolution_count against the array size, folded
into the existing zero-check.

When the WIN10 resolution probe fails, the caller in
hyperv_connect_vsp() left hv->screen_*_max / preferred_* unpopulated,
which sets mode_config.max_width / max_height to 0 and makes
drm_internal_framebuffer_create() reject every userspace framebuffer
with -EINVAL. The pre-WIN10 branch had the same gap for
preferred_width / preferred_height. Use a single post-probe fallback
guarded by screen_width_max == 0 so both paths converge on the WIN8
defaults.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-64524?


## How do I fix CVE-2026-64524?

Apply the vendor's patch.

## Is CVE-2026-64524 being exploited?

There is no known exploitation of CVE-2026-64524 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64524 and fix it if it is affected.

What it is: CVE-2026-64524 is a high-severity vulnerability in Linux, published on 25 Jul 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-2026-64524 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-2026-64524/ (Markdown: https://insights.sbomify.com/CVE-2026-64524/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64524
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64524
- OSV: https://osv.dev/vulnerability/CVE-2026-64524

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64524/
Summaries are generated and may contain mistakes; the official description above is the record.