# CVE-2021-47060: KVM: Stop looking for coalesced MMIO zones if the bus is destroyed

> A use-after-free vulnerability in the Linux kernel's KVM subsystem allows attackers to cause a denial of service via improper handling of coalesced MMIO zones.

- **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:** 29 Feb 2024
- **Updated:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2021-47060, GHSA-6x38-gwgp-2pcm, UBUNTU-CVE-2021-47060

## What is CVE-2021-47060?

CVE-2021-47060 is a high-severity use after free vulnerability in Linux kernel, published on 29 Feb 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:

KVM: Stop looking for coalesced MMIO zones if the bus is destroyed

Abort the walk of coalesced MMIO zones if kvm_io_bus_unregister_dev()
fails to allocate memory for the new instance of the bus.  If it can't
instantiate a new bus, unregister_dev() destroys all devices _except_ the
target device.   But, it doesn't tell the caller that it obliterated the
bus and invoked the destructor for all devices that were on the bus.  In
the coalesced MMIO case, this can result in a deleted list entry
dereference due to attempting to continue iterating on coalesced_zones
after future entries (in the walk) have been deleted.

Opportunistically add curly braces to the for-loop, which encompasses
many lines but sneaks by without braces due to the guts being a single
if statement.

## Which versions are affected by CVE-2021-47060?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47060?

Apply the vendor's patch.

## Is CVE-2021-47060 being exploited?

There is no known exploitation of CVE-2021-47060 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-2021-47060 and fix it if it is affected.

What it is: CVE-2021-47060 is a high-severity use after free vulnerability in Linux kernel, published on 29 Feb 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-2021-47060 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-2021-47060/ (Markdown: https://insights.sbomify.com/CVE-2021-47060/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47060
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47060
- OSV: https://osv.dev/vulnerability/CVE-2021-47060

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47060/
Summaries are generated and may contain mistakes; the official description above is the record.