High 7.8Published Apr 1, 2025

CVE-2025-21971net_sched: Prevent creation of classes with TC_H_ROOT

Updated under an hour ago (Oct 26, 2026, 7:10 PM ET)

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Exploited in the last 30 days

In the Linux kernel, the following vulnerability has been resolved: net_sched: Prevent creation of classes with TC_H_ROOT The function qdisc_tree_reduce_backlog() uses TC_H_ROOT as a termination condition when traversing up the qdisc tree to update parent backlog counters. However, if a class is created with classid TC_H_ROOT, the traversal terminates prematurely at this class instead of reaching the actual root qdisc, causing parent statistics to be incorrectly maintained. In case of DRR, this could lead to a crash as reported by Mingi Cho. Prevent the creation of any Qdisc class with classid TC_H_ROOT (0xFFFFFFFF) across all qdisc types, as suggested by Jamal.

CVSS: 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 15, 2026
First seen by InfoSec Signals: Oct 15, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from 066a3b5b2346febf9a655b444567b7138e3bb939 before e05d9938b1b0ac40b6054cc5fa0ccbd9afd5ed4c; 066a3b5b2346febf9a655b444567b7138e3bb939 builds before 7a82fe67a9f4d7123d8e5ba8f0f0806c28695006; 066a3b5b2346febf9a655b444567b7138e3bb939 builds before 003d92c91cdb5a64b25a9a74cb8543aac9a8bb48; from 066a3b5b2346febf9a655b444567b7138e3bb939 before e5ee00607bbfc97ef1526ea95b6b2458ac9e7cb7; from 066a3b5b2346febf9a655b444567b7138e3bb939 before 78533c4a29ac3aeddce4b481770beaaa4f3bfb67; 066a3b5b2346febf9a655b444567b7138e3bb939 builds before 5c3ca9cb48b51bd72bf76b8b05e24f3cd53db5e7; from 066a3b5b2346febf9a655b444567b7138e3bb939 before 94edfdfb9505ab608e86599d1d1e38c83816fc1c; 066a3b5b2346febf9a655b444567b7138e3bb939 builds before 0c3057a5a04d07120b3d0ec9c79568fceb9c921e	CNA record
linux linux_kernel linux:linux_kernel	from 2.6.26 before 5.4.292; from 5.5 before 5.10.236; from 5.11 before 5.15.180; from 5.16 before 6.1.132; from 6.2 before 6.6.84; from 6.7 before 6.12.20; from 6.13 before 6.13.8; 2.6.25; and 6 more ranges	NVD

References

References

https://git.kernel.org/stable/c/e05d9938b1b0ac40b6054cc5fa0ccbd9afd5ed4c	patch
https://git.kernel.org/stable/c/7a82fe67a9f4d7123d8e5ba8f0f0806c28695006	patch
https://git.kernel.org/stable/c/003d92c91cdb5a64b25a9a74cb8543aac9a8bb48	patch
https://git.kernel.org/stable/c/e5ee00607bbfc97ef1526ea95b6b2458ac9e7cb7	patch
https://git.kernel.org/stable/c/78533c4a29ac3aeddce4b481770beaaa4f3bfb67	patch
https://git.kernel.org/stable/c/5c3ca9cb48b51bd72bf76b8b05e24f3cd53db5e7	patch
https://git.kernel.org/stable/c/94edfdfb9505ab608e86599d1d1e38c83816fc1c	patch
https://git.kernel.org/stable/c/0c3057a5a04d07120b3d0ec9c79568fceb9c921e	patch
https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.