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Publication date: 2025-10-29

Last updated on: 2025-12-06

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_qfq: Fix null-deref in agg_dequeue To prevent a potential crash in agg_dequeue (net/sched/sch_qfq.c) when cl->qdisc->ops->peek(cl->qdisc) returns NULL, we check the return value before using it, similar to the existing approach in sch_hfsc.c. To avoid code duplication, the following changes are made: 1. Changed qdisc_warn_nonwc(include/net/pkt_sched.h) into a static inline function. 2. Moved qdisc_peek_len from net/sched/sch_hfsc.c to include/net/pkt_sched.h so that sch_qfq can reuse it. 3. Applied qdisc_peek_len in agg_dequeue to avoid crashing.

CVSS Scores

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Meta Information

Published

2025-10-29

Last Modified

2025-12-06

Generated

2026-07-06

AI Q&A

2025-10-29

EPSS Evaluated

2026-07-05

NVD

CVE-2025-40083

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability is a null pointer dereference in the Linux kernel's sch_qfq network scheduler code, specifically in the agg_dequeue function. It occurs when a function call returns NULL but the code does not check for this before using the returned value, which can cause a crash. The fix involves adding a check for NULL return values to prevent the crash.

Impact Analysis

This vulnerability can cause the Linux kernel to crash due to a null pointer dereference in the network scheduling code. Such a crash can lead to denial of service or system instability.

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