CVE Catalog

CVE-2025-21971

HighCVSS 7.8
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.20%

10th percentile - higher than 10% of all known CVEs

Summary

In the Linux kernel's net_sched subsystem, a vulnerability allows creating classes with the TC_H_ROOT identifier. This causes premature termination of qdisc tree traversal, leading to incorrect parent statistics and potential crashes in the DRR discipline.

Risk Assessment

The organization faces system instability and potential crashes due to incorrect network queue management, which may lead to service disruptions.

Recommendation

Immediately update the Linux kernel to a version containing the fix that prevents creation of classes with the TC_H_ROOT identifier.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS