# CVE-2026-98011: net/sched: hhf: clamp quantum in change and init paths

> A local attacker with CAP_NET_ADMIN can cause a kernel soft lockup and denial of service by setting a low quantum value in the HHF qdisc.

- **Severity:** Not scored
- **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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104574, BELL-CVE-2026-98011, DEBIAN-CVE-2026-98011, GHSA-93pc-w6vh-hg9r, UBUNTU-CVE-2026-98011

## What is CVE-2026-98011?

CVE-2026-98011 is a denial of service vulnerability in Linux, published on 25 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:

net/sched: hhf: clamp quantum in change and init paths

hhf_change() accepts any quantum from userspace, including 1. With a
crafted size table qdisc_pkt_len reaches ~2 GiB, so quantum=1 makes
the deficit-refill loop spin ~2^31 times under the qdisc lock
(a soft lockup / denial of service).

Add max(256U, ...) in hhf_change() matching fq_codel_change(). Clamp
hhf_init() to [256, 1<<20] matching the siblings, and remove the old
fallback that only set quantum=256 on overflow.

Conditions to recreate the bug:
  CONFIG_NET_SCH_HHF=y. Requires CAP_NET_ADMIN (namespace-local via
  unshare -Urn suffices).

  tc qdisc add dev dummy0 root hhf
  tc qdisc change dev dummy0 root hhf quantum 1 stab data 32768 size_log 15 cell_log 0

## Which versions are affected by CVE-2026-98011?


## How do I fix CVE-2026-98011?

Apply the vendor's patch.

## Is CVE-2026-98011 being exploited?

There is no known exploitation of CVE-2026-98011 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98011 and fix it if it is affected.

What it is: CVE-2026-98011 is a denial of service vulnerability in Linux, published on 25 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-2026-98011 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-2026-98011/ (Markdown: https://insights.sbomify.com/CVE-2026-98011/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98011
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98011
- OSV: https://osv.dev/vulnerability/CVE-2026-98011

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98011/
Summaries are generated and may contain mistakes; the official description above is the record.