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Fencer Vulns
medium 5.5

CVE-2025-38684 json

net/sched: ets: use old 'nbands' while purging unused classes

published 2025-09-04 14 mo ago modified 2026-11-05 3 d ago also EUVD-2025-26785

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 7%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

net/sched: ets: use old 'nbands' while purging unused classes

Shuang reported sch_ets test-case [1] crashing in ets_class_qlen_notify() after recent changes from Lion [2]. The problem is: in ets_qdisc_change() we purge unused DWRR queues; the value of 'q->nbands' is the new one, and the cleanup should be done with the old one. The problem is here since my first attempts to fix ets_qdisc_change(), but it surfaced again after the recent qdisc len accounting fixes. Fix it purging idle DWRR queues before assigning a new value of 'q->nbands', so that all purge operations find a consistent configuration:

- old 'q->nbands' because it's needed by ets_class_find() - old 'q->nstrict' because it's needed by ets_class_is_strict()

BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 62 UID: 0 PID: 39457 Comm: tc Kdump: loaded Not tainted 6.12.0-116.el10.x86_64 #1 PREEMPT(voluntary) Hardware name: Dell Inc. PowerEdge R640/06DKY5, BIOS 2.12.2 07/09/2021 RIP: 0010:__list_del_entry_valid_or_report+0x4/0x80 Code: ff 4c 39 c7 0f 84 39 19 8e ff b8 01 00 00 00 c3 cc cc cc cc 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa <48> 8b 17 48 8b 4f 08 48 85 d2 0f 84 56 19 8e ff 48 85 c9 0f 84 ab RSP: 0018:ffffba186009f400 EFLAGS: 00010202 RAX: 00000000000000d6 RBX: 0000000000000000 RCX: 0000000000000004 RDX: ffff9f0fa29b69c0 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffffffc12c2400 R08: 0000000000000008 R09: 0000000000000004 R10: ffffffffffffffff R11: 0000000000000004 R12: 0000000000000000 R13: ffff9f0f8cfe0000 R14: 0000000000100005 R15: 0000000000000000 FS: 00007f2154f37480(0000) GS:ffff9f269c1c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 00000001530be001 CR4: 00000000007726f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <TASK> ets_class_qlen_notify+0x65/0x90 [sch_ets] qdisc_tree_reduce_backlog+0x74/0x110 ets_qdisc_change+0x630/0xa40 [sch_ets] __tc_modify_qdisc.constprop.0+0x216/0x7f0 tc_modify_qdisc+0x7c/0x120 rtnetlink_rcv_msg+0x145/0x3f0 netlink_rcv_skb+0x53/0x100 netlink_unicast+0x245/0x390 netlink_sendmsg+0x21b/0x470 ____sys_sendmsg+0x39d/0x3d0 ___sys_sendmsg+0x9a/0xe0 __sys_sendmsg+0x7a/0xd0 do_syscall_64+0x7d/0x160 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7f2155114084 Code: 89 02 b8 ff ff ff ff eb bb 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 80 3d 25 f0 0c 00 00 74 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 48 83 ec 28 89 54 24 1c 48 89 RSP: 002b:00007fff1fd7a988 EFLAGS: 00000202 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000560ec063e5e0 RCX: 00007f2155114084 RDX: 0000000000000000 RSI: 00007fff1fd7a9f0 RDI: 0000000000000003 RBP: 00007fff1fd7aa60 R08: 0000000000000010 R09: 000000000000003f R10: 0000560ee9b3a010 R11: 0000000000000202 R12: 00007fff1fd7aae0 R13: 000000006891ccde R14: 0000560ec063e5e0 R15: 00007fff1fd7aad0 </TASK>

[1] https://lore.kernel.org/netdev/e08c7f4a6882f260011909a868311c6e9b54f3e4.1639153474.git.dcaratti@redhat.com/ [2] https://lore.kernel.org/netdev/d912cbd7-193b-4269-9857-525bee8bbb6a@gmail.com/

Patch / fix

  • Linux Linux 5.5, 5.10.241, 5.15.190, 6.1.149, 6.6.103, 6.12.43, 6.15.11, 6.16.2, 6.17
  • Siemens SIMATIC CN 4100 V5.0
  • linux Debian 12 6.1.153-1
  • linux Debian 13 6.12.43-1
  • linux Debian 14 6.16.3-1

debian advisories DEBIAN-CVE-2025-38684

  • linux Ubuntu 22.04 LTS 5.15.0-163.173
  • linux Ubuntu 24.04 LTS 6.8.0-100.100
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1097.104
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1046.49
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1097.106
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1047.50
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1093.99
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1043.48

ubuntu advisories UBUNTU-CVE-2025-38684

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 8 4.18.0-553.75.1.el8_10
  • perf RHEL 8 4.18.0-553.75.1.el8_10
  • bpftool RHEL 8 4.18.0-553.75.1.el8_10
  • kernel-core RHEL 8 4.18.0-553.75.1.el8_10
  • kernel-tools RHEL 8 4.18.0-553.75.1.el8_10
  • python3-perf RHEL 8 4.18.0-553.75.1.el8_10
  • kernel-modules RHEL 8 4.18.0-553.75.1.el8_10
  • kernel-zfcpdump RHEL 8 4.18.0-553.75.1.el8_10

red hat advisories RHSA-2025:15785RHSA-2025:15447RHSA-2025:15035RHSA-2025:15011

  • kernel-rt SLE Micro 5.4, SLE Micro 5.3 5.14.21-150400.15.145.1
  • kernel-source-rt SLE Micro 5.4, SLE Micro 5.3 5.14.21-150400.15.145.1
  • kernel-64kb SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS, SLE High Performance Computing 15 SP4-ESPOS 5.14.21-150400.24.194.1
  • kernel-syms SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +1 more 5.14.21-150400.24.194.1
  • kernel-source SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +1 more 5.14.21-150400.24.194.1
  • kernel-default SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE Micro 5.4 +5 more 5.14.21-150400.24.194.1
  • kernel-obs-build SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +1 more 5.14.21-150400.24.194.1
  • kernel-default-base SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE Micro 5.4 +3 more 5.14.21-150400.24.194.1.150400.24.98.3

suse advisories SUSE-SU-2026:1131-1SUSE-SU-2026:0617-1SUSE-SU-2026:0496-1SUSE-SU-2026:0474-1SUSE-SU-2025:21074-1SUSE-SU-2025:21139-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.6.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-kvmsmall openSUSE Leap 16.0 6.12.0-160000.6.1

opensuse advisories openSUSE-SU-2025:20081-1

  • kernel AlmaLinux 8 4.18.0-553.75.1.el8_10
  • perf AlmaLinux 8 4.18.0-553.75.1.el8_10
  • bpftool AlmaLinux 8 4.18.0-553.75.1.el8_10
  • kernel-core AlmaLinux 8 4.18.0-553.75.1.el8_10
  • kernel-tools AlmaLinux 8 4.18.0-553.75.1.el8_10
  • python3-perf AlmaLinux 8 4.18.0-553.75.1.el8_10
  • kernel-modules AlmaLinux 8 4.18.0-553.75.1.el8_10
  • kernel-zfcpdump AlmaLinux 8 4.18.0-553.75.1.el8_10

almalinux advisories ALSA-2025:15785ALSA-2025:15447ALSA-2025:15011

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-38684 updated cvss 5.2

kernel: net/sched: ets: use old 'nbands' while purging unused classes

  • Red Hat Enterprise Linux 8 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +6 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-570.39.1.el9_6, perf 5.14.0-570.39.1.el9_6, rtla 5.14.0-570.39.1.el9_6, python3-perf 5.14.0-570.39.1.el9_6, kernel-devel-matched 5.14.0-570.39.1.el9_6, kernel-64k-devel-matched 5.14.0-570.39.1.el9_6, +7 more
    fixed: vendor fix RHSA-2025:15011
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-55.31.1.el10_0, perf 6.12.0-55.31.1.el10_0, rtla 6.12.0-55.31.1.el10_0, python3-perf 6.12.0-55.31.1.el10_0, kernel-devel-matched 6.12.0-55.31.1.el10_0, kernel-64k-devel-matched 6.12.0-55.31.1.el10_0, +7 more
    fixed: vendor fix RHSA-2025:15447
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.75.1.el8_10, kernel 4.18.0-553.75.1.el8_10, bpftool 4.18.0-553.75.1.el8_10, kernel-core 4.18.0-553.75.1.el8_10, kernel-tools 4.18.0-553.75.1.el8_10, python3-perf 4.18.0-553.75.1.el8_10, +15 more
    fixed: vendor fix RHSA-2025:15785
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-570.39.1.el9_6, kernel-64k 5.14.0-570.39.1.el9_6, kernel-core 5.14.0-570.39.1.el9_6, kernel-tools 5.14.0-570.39.1.el9_6, kernel-modules 5.14.0-570.39.1.el9_6, kernel-64k-core 5.14.0-570.39.1.el9_6, +27 more
    fixed: vendor fix RHSA-2025:15011
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-55.31.1.el10_0, kernel-64k 6.12.0-55.31.1.el10_0, kernel-core 6.12.0-55.31.1.el10_0, kernel-tools 6.12.0-55.31.1.el10_0, kernel-modules 6.12.0-55.31.1.el10_0, kernel-64k-core 6.12.0-55.31.1.el10_0, +27 more
    fixed: vendor fix RHSA-2025:15447
  • Red Hat Enterprise Linux BaseOS AUS (v.8.4) perf 4.18.0-305.170.1.el8_4, kernel 4.18.0-305.170.1.el8_4, bpftool 4.18.0-305.170.1.el8_4, kernel-core 4.18.0-305.170.1.el8_4, kernel-tools 4.18.0-305.170.1.el8_4, python3-perf 4.18.0-305.170.1.el8_4, +8 more Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) perf 4.18.0-305.170.1.el8_4, kernel 4.18.0-305.170.1.el8_4, bpftool 4.18.0-305.170.1.el8_4, kernel-core 4.18.0-305.170.1.el8_4, kernel-tools 4.18.0-305.170.1.el8_4, python3-perf 4.18.0-305.170.1.el8_4, +8 more
    fixed: vendor fix RHSA-2025:15035
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-570.39.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.39.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.39.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.39.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.39.1.el9_6
    fixed: vendor fix RHSA-2025:15011
show 7 more
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-55.31.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.31.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.31.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.31.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.31.1.el10_0
    fixed: vendor fix RHSA-2025:15447
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.75.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.75.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.75.1.el8_10
    fixed: vendor fix RHSA-2025:15785
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-570.39.1.el9_6, kernel-rt-64k 5.14.0-570.39.1.el9_6, kernel-rt-core 5.14.0-570.39.1.el9_6, kernel-rt-modules 5.14.0-570.39.1.el9_6, kernel-rt-64k-core 5.14.0-570.39.1.el9_6, kernel-rt-debug-core 5.14.0-570.39.1.el9_6, +14 more
    fixed: vendor fix RHSA-2025:15011
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-55.31.1.el10_0, kernel-rt-64k 6.12.0-55.31.1.el10_0, kernel-rt-core 6.12.0-55.31.1.el10_0, kernel-rt-modules 6.12.0-55.31.1.el10_0, kernel-rt-64k-core 6.12.0-55.31.1.el10_0, kernel-rt-debug-core 6.12.0-55.31.1.el10_0, +14 more
    fixed: vendor fix RHSA-2025:15447
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-570.39.1.el9_6, kernel-rt-kvm 5.14.0-570.39.1.el9_6, kernel-rt-core 5.14.0-570.39.1.el9_6, kernel-rt-modules 5.14.0-570.39.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.39.1.el9_6, kernel-rt-debug-core 5.14.0-570.39.1.el9_6, +6 more
    fixed: vendor fix RHSA-2025:15011
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-55.31.1.el10_0, kernel-rt-kvm 6.12.0-55.31.1.el10_0, kernel-rt-core 6.12.0-55.31.1.el10_0, kernel-rt-modules 6.12.0-55.31.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.31.1.el10_0, kernel-rt-debug-core 6.12.0-55.31.1.el10_0, +6 more
    fixed: vendor fix RHSA-2025:15447
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 d ago

Exploit prediction

0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux
  • Siemens SIMATIC CN 4100

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.