# CVE-2021-47228: x86/ioremap: Map EFI-reserved memory as encrypted for SEV

> A Linux kernel bug causes a crash during boot when mapping EFI-reserved memory as unencrypted in SEV environments.

- **Severity:** Medium 6.2 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/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:** 21 May 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47228, GHSA-w5h9-gvgr-jhpg, UBUNTU-CVE-2021-47228

## What is CVE-2021-47228?

CVE-2021-47228 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 May 2024. 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:

x86/ioremap: Map EFI-reserved memory as encrypted for SEV

Some drivers require memory that is marked as EFI boot services
data. In order for this memory to not be re-used by the kernel
after ExitBootServices(), efi_mem_reserve() is used to preserve it
by inserting a new EFI memory descriptor and marking it with the
EFI_MEMORY_RUNTIME attribute.

Under SEV, memory marked with the EFI_MEMORY_RUNTIME attribute needs to
be mapped encrypted by Linux, otherwise the kernel might crash at boot
like below:

  EFI Variables Facility v0.08 2004-May-17
  general protection fault, probably for non-canonical address 0x3597688770a868b2: 0000 [#1] SMP NOPTI
  CPU: 13 PID: 1 Comm: swapper/0 Not tainted 5.12.4-2-default #1 openSUSE Tumbleweed
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
  RIP: 0010:efi_mokvar_entry_next
  [...]
  Call Trace:
   efi_mokvar_sysfs_init
   ? efi_mokvar_table_init
   do_one_initcall
   ? __kmalloc
   kernel_init_freeable
   ? rest_init
   kernel_init
   ret_from_fork

Expand the __ioremap_check_other() function to additionally check for
this other type of boot data reserved at runtime and indicate that it
should be mapped encrypted for an SEV guest.

 [ bp: Massage commit message. ]

## Which versions are affected by CVE-2021-47228?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47228?

Apply the vendor's patch.

## Is CVE-2021-47228 being exploited?

There is no known exploitation of CVE-2021-47228 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-2021-47228 and fix it if it is affected.

What it is: CVE-2021-47228 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 May 2024. 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-2021-47228 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-2021-47228/ (Markdown: https://insights.sbomify.com/CVE-2021-47228/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47228
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47228
- OSV: https://osv.dev/vulnerability/CVE-2021-47228

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47228/
Summaries are generated and may contain mistakes; the official description above is the record.