CVE-2025-40083 Affecting linux-6.1 package, versions <6.1.159-1~deb11u1


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.21% (10th percentile)

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  • Snyk IDSNYK-DEBIAN11-LINUX61-14954690
  • published15 Jan 2026
  • disclosed29 Oct 2025

Introduced: 29 Oct 2025

CVE-2025-40083  (opens in a new tab)

How to fix?

Upgrade Debian:11 linux-6.1 to version 6.1.159-1~deb11u1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream linux-6.1 package and not the linux-6.1 package as distributed by Debian. See How to fix? for Debian:11 relevant fixed versions and status.

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 Base Scores

version 3.1