CVE-2025-21971
net_sched: Prevent creation of classes with TC_H_ROOT
MEDIUM 5.5EPSS 0.2%
In the Linux kernel, the following vulnerability has been resolved:net_sched: Prevent creation of classes with TC_H_ROOTThe function qdisc_tree_reduce_backlog() uses TC_H_ROOT as a terminationcondition when traversing up the qdisc tree to update parent backlogcounters. However, if a class is created with classid TC_H_ROOT, thetraversal terminates prematurely at this class instead of reaching theactual 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.
- Affected
- Linux
- CVSS v3.1 NVD
- 5.5 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - CVSS v3.1 CNA
- 7.8 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - EPSS
- 0.22% chance of exploitation in the next 30 days, 12th percentile
- Published
- 2025-04-01
- Updated
- 2026-10-15
Exploit collections (1)
- linux/kernelctf/CVE-2025-21971_lts_cos_mitigationgoogle/security-research
Security advisories
- https://git.kernel.org/stable/c/003d92c91cdb5a64b25a9a74cb8543aac9a8bb48
- https://git.kernel.org/stable/c/0c3057a5a04d07120b3d0ec9c79568fceb9c921e
- https://git.kernel.org/stable/c/5c3ca9cb48b51bd72bf76b8b05e24f3cd53db5e7
- https://git.kernel.org/stable/c/78533c4a29ac3aeddce4b481770beaaa4f3bfb67
- https://git.kernel.org/stable/c/7a82fe67a9f4d7123d8e5ba8f0f0806c28695006
- https://git.kernel.org/stable/c/94edfdfb9505ab608e86599d1d1e38c83816fc1c
- https://git.kernel.org/stable/c/e05d9938b1b0ac40b6054cc5fa0ccbd9afd5ed4c
- https://git.kernel.org/stable/c/e5ee00607bbfc97ef1526ea95b6b2458ac9e7cb7