# CVE-2021-46969: bus: mhi: core: Fix invalid error returning in mhi_queue

> A use-after-free vulnerability in the Linux kernel MHI bus driver allows attackers to potentially execute code or cause a denial of service.

- **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:** No
- **Published:** 27 Feb 2024
- **Updated:** 5 Aug 2026
- **Also known as:** GHSA-c4q6-cxg2-pxc8, UBUNTU-CVE-2021-46969

## What is CVE-2021-46969?

CVE-2021-46969 is a high-severity use after free vulnerability in Linux kernel, published on 27 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:

bus: mhi: core: Fix invalid error returning in mhi_queue

mhi_queue returns an error when the doorbell is not accessible in
the current state. This can happen when the device is in non M0
state, like M3, and needs to be waken-up prior ringing the DB. This
case is managed earlier by triggering an asynchronous M3 exit via
controller resume/suspend callbacks, that in turn will cause M0
transition and DB update.

So, since it's not an error but just delaying of doorbell update, there
is no reason to return an error.

This also fixes a use after free error for skb case, indeed a caller
queuing skb will try to free the skb if the queueing fails, but in
that case queueing has been done.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-46969?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-46969?

No fix has been published for CVE-2021-46969 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-46969 being exploited?

There is no known exploitation of CVE-2021-46969 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-2021-46969 and fix it if it is affected.

What it is: CVE-2021-46969 is a high-severity use after free vulnerability in Linux kernel, published on 27 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-2021-46969 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-2021-46969/ (Markdown: https://insights.sbomify.com/CVE-2021-46969/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-46969
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-46969
- OSV: https://osv.dev/vulnerability/CVE-2021-46969

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-46969/
Summaries are generated and may contain mistakes; the official description above is the record.