# CVE-2021-46945: ext4: always panic when errors=panic is specified

> A regression in the Linux kernel ext4 filesystem prevented panics when errors=panic was set, allowing potential denial of service under specific mount conditions.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 11 May 2026
- **Also known as:** GHSA-hx29-fw56-x5wj, UBUNTU-CVE-2021-46945

## What is CVE-2021-46945?

CVE-2021-46945 is a medium-severity denial of service 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:

ext4: always panic when errors=panic is specified

Before commit 014c9caa29d3 ("ext4: make ext4_abort() use
__ext4_error()"), the following series of commands would trigger a
panic:

1. mount /dev/sda -o ro,errors=panic test
2. mount /dev/sda -o remount,abort test

After commit 014c9caa29d3, remounting a file system using the test
mount option "abort" will no longer trigger a panic.  This commit will
restore the behaviour immediately before commit 014c9caa29d3.
(However, note that the Linux kernel's behavior has not been
consistent; some previous kernel versions, including 5.4 and 4.19
similarly did not panic after using the mount option "abort".)

This also makes a change to long-standing behaviour; namely, the
following series commands will now cause a panic, when previously it
did not:

1. mount /dev/sda -o ro,errors=panic test
2. echo test > /sys/fs/ext4/sda/trigger_fs_error

However, this makes ext4's behaviour much more consistent, so this is
a good thing.

## Which versions are affected by CVE-2021-46945?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-46945?

No fix has been published for CVE-2021-46945 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-46945 being exploited?

There is no known exploitation of CVE-2021-46945 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-2021-46945 and fix it if it is affected.

What it is: CVE-2021-46945 is a medium-severity denial of service 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-2021-46945 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-2021-46945/ (Markdown: https://insights.sbomify.com/CVE-2021-46945/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-46945
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-46945
- OSV: https://osv.dev/vulnerability/CVE-2021-46945

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-46945/
Summaries are generated and may contain mistakes; the official description above is the record.