# CVE-2026-46121: mm/damon/sysfs-schemes: protect memcg_path kfree() with damon_sysfs_lock

> A race condition in the Linux kernel DAMON sysfs interface allows local attackers to trigger a use-after-free, potentially leading to code execution or privilege escalation.

- **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:** 28 May 2026
- **Updated:** 14 Jun 2026
- **Also known as:** BELL-CVE-2026-46121, DEBIAN-CVE-2026-46121, GHSA-496c-fq9m-2rhq, ROOT-OS-UBUNTU-2404-CVE-2026-46121, UBUNTU-CVE-2026-46121

## What is CVE-2026-46121?

CVE-2026-46121 is a high-severity use after free vulnerability in Linux kernel, published on 28 May 2026. 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:

mm/damon/sysfs-schemes: protect memcg_path kfree() with damon_sysfs_lock

Patch series "mm/damon/sysfs-schemes: fix use-after-free for [memcg_]path".

Reads of 'memcg_path' and 'path' files in DAMON sysfs interface could race
with their writes, results in use-after-free.  Fix those.

This patch (of 2):

damon_sysfs_scheme_filter->mmecg_path can be read and written by users,
via DAMON sysfs memcg_path file.  It can also be indirectly read, for the
parameters {on,off}line committing to DAMON.  The reads for parameters
committing are protected by damon_sysfs_lock to avoid the sysfs files
being destroyed while any of the parameters are being read.  But the
user-driven direct reads and writes are not protected by any lock, while
the write is deallocating the memcg_path-pointing buffer.  As a result,
the readers could read the already freed buffer (user-after-free).  Note
that the user-reads don't race when the same open file is used by the
writer, due to kernfs's open file locking.  Nonetheless, doing the reads
and writes with separate open files would be common.  Fix it by protecting
both the user-direct reads and writes with damon_sysfs_lock.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-46121?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-46121?

Apply the vendor's patch.

## Is CVE-2026-46121 being exploited?

There is no known exploitation of CVE-2026-46121 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-2026-46121 and fix it if it is affected.

What it is: CVE-2026-46121 is a high-severity use after free vulnerability in Linux kernel, published on 28 May 2026. 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-2026-46121 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-2026-46121/ (Markdown: https://insights.sbomify.com/CVE-2026-46121/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46121
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46121
- OSV: https://osv.dev/vulnerability/CVE-2026-46121

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46121/
Summaries are generated and may contain mistakes; the official description above is the record.