High 7.8Published Jun 6, 2025

CVE-2025-38000sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue()

Updated under an hour ago (Oct 27, 2026, 7:00 PM ET)

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Exploited in the last 30 days

In the Linux kernel, the following vulnerability has been resolved: sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue() When enqueuing the first packet to an HFSC class, hfsc_enqueue() calls the child qdisc's peek() operation before incrementing sch->q.qlen and sch->qstats.backlog. If the child qdisc uses qdisc_peek_dequeued(), this may trigger an immediate dequeue and potential packet drop. In such cases, qdisc_tree_reduce_backlog() is called, but the HFSC qdisc's qlen and backlog have not yet been updated, leading to inconsistent queue accounting. This can leave an empty HFSC class in the active list, causing further consequences like use-after-free. This patch fixes the bug by moving the increment of sch->q.qlen and sch->qstats.backlog before the call to the child qdisc's peek() operation. This ensures that queue length and backlog are always accurate when packet drops or dequeues are triggered during the peek.

CVSS: 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 15, 2026
First seen by InfoSec Signals: Oct 15, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 before 1034e3310752e8675e313f7271b348914008719a; from 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 before f9f593e34d2fb67644372c8f7b033bdc622ad228; from 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 before 89c301e929a0db14ebd94b4d97764ce1d6981653; from 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 before f1dde3eb17dc1b8bd07aed00004b1e05fc87a3d4; from 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 before 93c276942e75de0e5bc91576300d292e968f5a02; from 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 before 49b21795b8e5654a7df3d910a12e1060da4c04cf; 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 builds before 3f3a22eebbc32b4fa8ce9c1d5f9db214b45b9335; 12d0ad3be9c3854e52ec74bb83bb6f43612827c7 builds before 3f981138109f63232a5fb7165938d4c945cc1b9d	CNA record
linux linux_kernel linux:linux_kernel	from 4.8 before 5.4.294; from 5.5 before 5.10.238; from 5.11 before 5.15.185; from 5.16 before 6.1.141; from 6.2 before 6.6.93; from 6.7 before 6.12.31; from 6.13 before 6.14.9; 6.15; and 6 more ranges	NVD
debian debian_linux debian:debian_linux	11.0	NVD

References

References

https://git.kernel.org/stable/c/1034e3310752e8675e313f7271b348914008719a	patch
https://git.kernel.org/stable/c/f9f593e34d2fb67644372c8f7b033bdc622ad228	patch
https://git.kernel.org/stable/c/89c301e929a0db14ebd94b4d97764ce1d6981653	patch
https://git.kernel.org/stable/c/f1dde3eb17dc1b8bd07aed00004b1e05fc87a3d4	patch
https://git.kernel.org/stable/c/93c276942e75de0e5bc91576300d292e968f5a02	patch
https://git.kernel.org/stable/c/49b21795b8e5654a7df3d910a12e1060da4c04cf	patch
https://git.kernel.org/stable/c/3f3a22eebbc32b4fa8ce9c1d5f9db214b45b9335	patch
https://git.kernel.org/stable/c/3f981138109f63232a5fb7165938d4c945cc1b9d	patch
https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html	third-party-advisory
https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html	third-party-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.