AUGUST 4, 2026
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Case File

CVE-2025-21971

HIGH · CVSS 7.8 EPSS 0.21%

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2025-04-01 · Last synced 2026-08-04

CyberRota Analysis

This is a high severity vulnerability with a CVSS score of 7.8. It affects Linux.

CVE
CVE-2025-21971
Severity
HIGH
CVSS
7.8
EPSS
0.21%
Linux

Original NVD Description

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.

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