CVE-2025-38477: net/sched: sch_qfq: Fix race condition on qfq_aggregate

Severity: medium (CVSS 4.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-07-28 · updated 2026-07-30
Weakness: CWE-362

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_qfq: Fix race condition on qfq_aggregate A race condition can occur when 'agg' is modified in qfq_change_agg (called during qfq_enqueue) while other threads access it concurrently. For example, qfq_dump_class may trigger a NULL dereference, and qfq_delete_class may cause a use-after-free. This patch addresses the issue by: 1. Moved qfq_destroy_class into the critical section. 2. Added sch_tree_lock protection to qfq_dump_class and qfq_dump_class_stats.

Affected products

Debian Linux: 11.0
Linux kernel: from 3.8 before 5.4.297; from 5.5 before 5.10.241; from 5.11 before 5.15.190; from 5.16 before 6.1.147; from 6.2 before 6.6.100; from 6.7 before 6.12.40 — fixed in 5.10.241, 5.15.190, 5.4.297, 6.1.147, 6.12.40, 6.15.8

How to fix

Upgrade to a fixed version: Linux kernel 5.10.241, 5.15.190, 5.4.297, 6.1.147. Check the vendor advisory for mitigations.

References

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