# CVE-2026-90005: samples/damon/wsse: handle damon_start() failure

> A local attacker with admin privileges can trigger a memory leak and potential use-after-free in the DAMON wsse sample module, leading to denial of service or privilege escalation.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-90005, DEBIAN-CVE-2026-90005, GHSA-rjc9-q3q5-8f95, UBUNTU-CVE-2026-90005

## What is CVE-2026-90005?

CVE-2026-90005 is a memory corruption vulnerability in Linux, published on 16 Sep 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:

samples/damon/wsse: handle damon_start() failure

Patch series "samples/damon: handle damon_{start,stop}() failures".

All DAMON sample modules are not correctly handling failures from
damon_start().  Among those, mtier also has an additional problem for
handling of damon_stop() failures.  wsse and prcl also have a problem in
their damon_call() failure handling.  As a result, memory leaks, next
DAMON operation disruptions, and use-after-free can happen.  Fix those.

Note that only the damon_start() failure caused issues can reliably be
reproduced.  Reproducing those issues require the admin permission,
though.

This patch (of 6):

damon_sample_wsse_start() callers assume it will clean up resources when
it fails.  And the function does the cleanup for context buildup failures.
However, it is not doing the cleanup for damon_start() failure.  As a
result, when damon_start() fails, it leaks the memory for DAMON context. 
Free the context in case of the failure to fix the issues.

Note that the issue can reliably be reproduced because the module calls
damon_start() in the exclusive mode.  For example,

    $ sudo damo start
    $ echo $$ | sudo tee /sys/module/damon_sample_wsse/parameters/target_pid
    $ echo Y | sudo tee /sys/module/damon_sample_wsse/parameters/enabled
    $ sudo cat /proc/allocinfo | grep damon_new_ctx

Because the first command is running another DAMON instance, the third
command fails the damon_start() call because the new DAMON instance cannot
exclusively run.  And without this fix, by repeating the third and the
fourth commands above, we can show the memory consumption is only
increasing due to the leaks.  It requires the sudo permission though.

The issue was discovered [1] by Sashiko.

## Which versions are affected by CVE-2026-90005?


## How do I fix CVE-2026-90005?

Apply the vendor's patch.

## Is CVE-2026-90005 being exploited?

There is no known exploitation of CVE-2026-90005 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90005 and fix it if it is affected.

What it is: CVE-2026-90005 is a memory corruption vulnerability in Linux, published on 16 Sep 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-2026-90005 in the wild and no public exploit code.

Affected product: Linux. 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-2026-90005/ (Markdown: https://insights.sbomify.com/CVE-2026-90005/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90005
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90005
- OSV: https://osv.dev/vulnerability/CVE-2026-90005

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90005/
Summaries are generated and may contain mistakes; the official description above is the record.