CVE-2025-37992: net_sched: Flush gso_skb list too during ->change()

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-05-26 · updated 2026-06-17
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: net_sched: Flush gso_skb list too during ->change() Previously, when reducing a qdisc's limit via the ->change() operation, only the main skb queue was trimmed, potentially leaving packets in the gso_skb list. This could result in NULL pointer dereference when we only check sch->limit against sch->q.qlen. This patch introduces a new helper, qdisc_dequeue_internal(), which ensures both the gso_skb list and the main queue are properly flushed when trimming excess packets. All relevant qdiscs (codel, fq, fq_codel, fq_pie, hhf, pie) are updated to use this helper in their ->change() routines.

Affected products

Debian Linux: 11.0
Linux kernel: from 3.5 before 5.10.238; from 5.11 before 5.15.184; from 5.16 before 6.1.140; from 6.2 before 6.6.92; from 6.7 before 6.12.30; from 6.13 before 6.14.8 — fixed in 5.10.238, 5.15.184, 6.1.140, 6.12.30, 6.14.8, 6.6.92

How to fix

Upgrade to a fixed version: Linux kernel 5.10.238, 5.15.184, 6.1.140, 6.12.30. Check the vendor advisory for mitigations.

References

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