# CVE-2026-74670: ipvs: stop estimator after disabled calc phase

> A race condition in the Linux kernel IPVS estimator allows out-of-bounds writes during namespace teardown, potentially causing 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:** Yes
- **Published:** 22 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** AZL-97365, BELL-CVE-2026-74670, DEBIAN-CVE-2026-74670, GHSA-98mw-8627-45gg, UBUNTU-CVE-2026-74670

## What is CVE-2026-74670?

CVE-2026-74670 is a high-severity 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:

ipvs: stop estimator after disabled calc phase

IPVS estimator kthread 0 starts with zeroed chain and tick limits until
its initial calculation phase completes. If network namespace teardown
clears ipvs->enable during that phase, ip_vs_est_calc_phase() can return
without installing positive limits.

The kthread can then continue into its main loop and drain
est_temp_list with zero chain_max, tick_max and est_max_count values.
Each enqueue consumes one available tick row, but est_count never
reaches the zero est_max_count value. After all rows are consumed, the
row lookup returns IPVS_EST_NTICKS and ip_vs_enqueue_estimator() writes
past the ticks and tick_len arrays.

Exit kthread 0 after the calculation phase if the kthread is stopping or
IPVS has been disabled. That keeps temporary estimators from being
drained after the limits failed to initialize.

Estimator kthreads can now self-exit before teardown or reload stops
kd->task. Keep an extra task reference after creation and release it
with kthread_stop_put(), so kd->task remains valid until the stop paths
consume that reference.

## Which versions are affected by CVE-2026-74670?


## How do I fix CVE-2026-74670?

Apply the vendor's patch.

## Is CVE-2026-74670 being exploited?

There is no known exploitation of CVE-2026-74670 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74670 and fix it if it is affected.

What it is: CVE-2026-74670 is a high-severity 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-2026-74670 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-2026-74670/ (Markdown: https://insights.sbomify.com/CVE-2026-74670/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74670
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74670
- OSV: https://osv.dev/vulnerability/CVE-2026-74670

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74670/
Summaries are generated and may contain mistakes; the official description above is the record.