# CVE-2026-74643: samples/damon/mtier: error out for zero quota goal target values

> A local attacker with root privileges can cause a kernel crash by setting specific DAMON sample module parameters to zero, triggering a division by zero error.

- **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:** 22 Aug 2026
- **Updated:** 22 Aug 2026
- **Also known as:** BELL-CVE-2026-74643, DEBIAN-CVE-2026-74643, GHSA-4gjp-m56q-x3cm, UBUNTU-CVE-2026-74643

## What is CVE-2026-74643?

CVE-2026-74643 is a denial of service vulnerability in Linux, published on 22 Aug 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/mtier: error out for zero quota goal target values

Patch series "mm/damon: avoid division by zero from damos_quota_score()".

DAMON_SAMPLE_MTIER and DAMON_LRU_SORT allow the user to trigger division
by zero in damos_quota_score().  Avoid it by adding parameters validation
checks.

This patch (of 2):

damos_quota_score() can trigger division by zero if the target_value is
zero.  DAMON_SAMPLE_MTIER lets users set the target_value via
node0_mem_{used,free}_bp parameters.  It doesn't guard zero value case,
though.  As a result, users can trigger division by zero.  Fix the issue
by returning an error when the user tries to start DAMON with zero
node0_mem_{used,free}_bp parameter values.

DAMON_SAMPLE_MTIER is just a sample module, but the consequence is quite
bad.  Also the zero node0_mem_free_bp parameter might look like a
reasonable setup to some users.  Hence, the issue might really happen in
the real world.

One reliable way to reproduce the issue is like below:

    # cd /sys/module/damon_sample_mtier/parameters
    # echo 4096 > node0_start_addr
    # echo 8192 > node0_end_addr
    # echo 8192 > node1_start_addr
    # echo 81920 > node1_end_addr
    # echo 0 > node0_mem_free_bp
    # echo Y > enabled
    # dmesg -w
    [...]
    [18792.235916] Oops: divide error: 0000 [#1] SMP NOPTI
    [...]
    [18792.242787] RIP: 0010:damos_quota_score+0x6f/0x480
    [...]

This issue was discovered [1] by Sashiko.

## Which versions are affected by CVE-2026-74643?


## How do I fix CVE-2026-74643?

Apply the vendor's patch.

## Is CVE-2026-74643 being exploited?

There is no known exploitation of CVE-2026-74643 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74643 and fix it if it is affected.

What it is: CVE-2026-74643 is a denial of service vulnerability in Linux, published on 22 Aug 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-2026-74643 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-2026-74643/ (Markdown: https://insights.sbomify.com/CVE-2026-74643/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74643
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74643
- OSV: https://osv.dev/vulnerability/CVE-2026-74643

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74643/
Summaries are generated and may contain mistakes; the official description above is the record.