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Fencer Vulns
high 7.8

CVE-2026-23074 json

net/sched: Enforce that teql can only be used as root qdisc

published 2026-02-04 9 mo ago modified 2026-10-19 20 d ago also EUVD-2026-5470

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 8%
public exploits
0
none known

Summary

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

net/sched: Enforce that teql can only be used as root qdisc

Design intent of teql is that it is only supposed to be used as root qdisc. We need to check for that constraint.

Although not important, I will describe the scenario that unearthed this issue for the curious.

GangMin Kim <km.kim1503@gmail.com> managed to concot a scenario as follows:

ROOT qdisc 1:0 (QFQ) ├── class 1:1 (weight=15, lmax=16384) netem with delay 6.4s └── class 1:2 (weight=1, lmax=1514) teql

GangMin sends a packet which is enqueued to 1:1 (netem). Any invocation of dequeue by QFQ from this class will not return a packet until after 6.4s. In the meantime, a second packet is sent and it lands on 1:2. teql's enqueue will return success and this will activate class 1:2. Main issue is that teql only updates the parent visible qlen (sch->q.qlen) at dequeue. Since QFQ will only call dequeue if peek succeeds (and teql's peek always returns NULL), dequeue will never be called and thus the qlen will remain as 0. With that in mind, when GangMin updates 1:2's lmax value, the qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc's qlen was not incremented, qfq fails to deactivate the class, but still frees its pointers from the aggregate. So when the first packet is rescheduled after 6.4 seconds (netem's delay), a dangling pointer is accessed causing GangMin's causing a UAF.

Patch / fix

  • Linux Linux 5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.68, 6.18.8, 6.19
  • Red Hat Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSION 0:2.6.32-754.59.1.el6
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:3.10.0-1160.147.1.el7, 0:3.10.0-1160.147.1.rt56.1299.el7
  • Red Hat Red Hat Enterprise Linux 8 0:4.18.0-553.107.1.el8_10, 0:4.18.0-553.107.1.rt7.448.el8_10
  • Red Hat Red Hat Enterprise Linux 8.2 Advanced Update Support 0:4.18.0-193.187.1.el8_2
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 0:4.18.0-305.186.1.el8_4
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 0:4.18.0-305.186.1.el8_4
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 0:4.18.0-372.181.1.el8_6
  • Red Hat Red Hat Enterprise Linux 8.6 Telecommunications Update Service 0:4.18.0-372.181.1.el8_6
  • Red Hat Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions 0:4.18.0-372.181.1.el8_6
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service 0:4.18.0-477.130.1.el8_8
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 0:4.18.0-477.130.1.el8_8
  • linux Debian 12 6.1.162-1
  • linux Debian 13 6.12.69-1
  • linux Debian 14 6.18.8-1

debian advisories DEBIAN-CVE-2026-23074

  • linux Ubuntu 22.04 LTS 5.15.0-174.184
  • linux Ubuntu 24.04 LTS 6.8.0-107.107
  • linux Ubuntu 25.10 6.17.0-20.20
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1104.111
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1051.54
  • linux-aws Ubuntu 25.10 6.17.0-1010.10
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1104.113
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1053.56

ubuntu advisories UBUNTU-CVE-2026-23074

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-rt RHEL 8 4.18.0-553.107.1.rt7.448.el8_10
  • kernel-rt-kvm RHEL 8 4.18.0-553.107.1.rt7.448.el8_10
  • kernel-rt-core RHEL 8 4.18.0-553.107.1.rt7.448.el8_10
  • kernel-rt-modules RHEL 8 4.18.0-553.107.1.rt7.448.el8_10
  • kernel-rt-debug-kvm RHEL 8 4.18.0-553.107.1.rt7.448.el8_10
  • kernel-rt-debug-core RHEL 8 4.18.0-553.107.1.rt7.448.el8_10
  • kernel-rt-debug-modules RHEL 8 4.18.0-553.107.1.rt7.448.el8_10
  • kernel-rt-modules-extra RHEL 8 4.18.0-553.107.1.rt7.448.el8_10

red hat advisories RHSA-2026:3810RHSA-2026:3685RHSA-2026:3634RHSA-2026:3388RHSA-2026:3360RHSA-2026:3277

  • kernel-livepatch-SLE16_Update_2 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 5-160000.1.1
  • kernel-livepatch-SLE16_Update_3 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 4-160000.1.1
  • kernel-livepatch-SLE16_Update_1 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 7-160000.1.1
  • kernel-livepatch-SLE16_Update_5 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 2-160000.1.1
  • kgraft-patch-SLE12-SP5_Update_76 SLE Live Patching 12 SP5 4-2.1
  • kgraft-patch-SLE12-SP5_Update_73 SLE Live Patching 12 SP5 6-2.1
  • kgraft-patch-SLE12-SP5_Update_72 SLE Live Patching 12 SP5 8-2.1
  • kgraft-patch-SLE12-SP5_Update_71 SLE Live Patching 12 SP5 9-2.1

suse advisories SUSE-SU-2026:1305-1SUSE-SU-2026:1304-1SUSE-SU-2026:1298-1SUSE-SU-2026:1297-1SUSE-SU-2026:1294-1SUSE-SU-2026:21102-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.27.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.27.1

opensuse advisories openSUSE-SU-2026:20416-1

  • kernel AlmaLinux 8 4.18.0-553.107.1.el8_10
  • perf AlmaLinux 8 4.18.0-553.107.1.el8_10
  • bpftool AlmaLinux 8 4.18.0-553.107.1.el8_10
  • kernel-core AlmaLinux 8 4.18.0-553.107.1.el8_10
  • kernel-tools AlmaLinux 8 4.18.0-553.107.1.el8_10
  • python3-perf AlmaLinux 8 4.18.0-553.107.1.el8_10
  • kernel-modules AlmaLinux 8 4.18.0-553.107.1.el8_10
  • kernel-zfcpdump AlmaLinux 8 4.18.0-553.107.1.el8_10

almalinux advisories ALSA-2026:3083ALSA-2026:3110

  • kernel Azure Linux 3.0 6.6.126.1-1

azure linux advisories AZL-77238

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-23074 updated cvss 7.0

kernel: Linux kernel: Use-after-free in teql queueing discipline can lead to privilege escalation

  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.107.1.el8_10, kernel 4.18.0-553.107.1.el8_10, bpftool 4.18.0-553.107.1.el8_10, kernel-core 4.18.0-553.107.1.el8_10, kernel-tools 4.18.0-553.107.1.el8_10, python3-perf 4.18.0-553.107.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:3083
  • Red Hat Enterprise Linux BaseOS AUS (v. 8.2) perf 4.18.0-193.187.1.el8_2, kernel 4.18.0-193.187.1.el8_2, bpftool 4.18.0-193.187.1.el8_2, kernel-core 4.18.0-193.187.1.el8_2, kernel-tools 4.18.0-193.187.1.el8_2, python3-perf 4.18.0-193.187.1.el8_2, +8 more
    fixed: vendor fix RHSA-2026:3388
  • Red Hat Enterprise Linux BaseOS AUS (v.8.4) perf 4.18.0-305.186.1.el8_4, kernel 4.18.0-305.186.1.el8_4, bpftool 4.18.0-305.186.1.el8_4, kernel-core 4.18.0-305.186.1.el8_4, kernel-tools 4.18.0-305.186.1.el8_4, python3-perf 4.18.0-305.186.1.el8_4, +8 more
    fixed: vendor fix RHSA-2026:3360
  • Red Hat Enterprise Linux BaseOS AUS (v.8.6) perf 4.18.0-372.181.1.el8_6, kernel 4.18.0-372.181.1.el8_6, bpftool 4.18.0-372.181.1.el8_6, kernel-core 4.18.0-372.181.1.el8_6, kernel-tools 4.18.0-372.181.1.el8_6, python3-perf 4.18.0-372.181.1.el8_6, +8 more Red Hat Enterprise Linux BaseOS E4S (v.8.6) perf 4.18.0-372.181.1.el8_6, kernel 4.18.0-372.181.1.el8_6, bpftool 4.18.0-372.181.1.el8_6, kernel-core 4.18.0-372.181.1.el8_6, kernel-tools 4.18.0-372.181.1.el8_6, python3-perf 4.18.0-372.181.1.el8_6, +15 more
    fixed: vendor fix RHSA-2026:3268
  • Red Hat Enterprise Linux BaseOS E4S (v.8.8) perf 4.18.0-477.130.1.el8_8, kernel 4.18.0-477.130.1.el8_8, bpftool 4.18.0-477.130.1.el8_8, kernel-core 4.18.0-477.130.1.el8_8, kernel-tools 4.18.0-477.130.1.el8_8, python3-perf 4.18.0-477.130.1.el8_8, +9 more
    fixed: vendor fix RHSA-2026:3277
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) perf 4.18.0-305.186.1.el8_4, kernel 4.18.0-305.186.1.el8_4, bpftool 4.18.0-305.186.1.el8_4, kernel-core 4.18.0-305.186.1.el8_4, kernel-tools 4.18.0-305.186.1.el8_4, python3-perf 4.18.0-305.186.1.el8_4, +8 more
    fixed: vendor fix RHSA-2026:3360
  • Red Hat Enterprise Linux BaseOS TUS (v.8.6) perf 4.18.0-372.181.1.el8_6, kernel 4.18.0-372.181.1.el8_6, bpftool 4.18.0-372.181.1.el8_6, kernel-core 4.18.0-372.181.1.el8_6, kernel-tools 4.18.0-372.181.1.el8_6, python3-perf 4.18.0-372.181.1.el8_6, +8 more
    fixed: vendor fix RHSA-2026:3268
  • Red Hat Enterprise Linux BaseOS TUS (v.8.8) perf 4.18.0-477.130.1.el8_8, kernel 4.18.0-477.130.1.el8_8, bpftool 4.18.0-477.130.1.el8_8, kernel-core 4.18.0-477.130.1.el8_8, kernel-tools 4.18.0-477.130.1.el8_8, python3-perf 4.18.0-477.130.1.el8_8, +8 more
    fixed: vendor fix RHSA-2026:3277
show 8 more
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.107.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.107.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.107.1.el8_10
    fixed: vendor fix RHSA-2026:3083
  • Red Hat Enterprise Linux for Real Time (v. 7 ELS) kernel-rt 3.10.0-1160.147.1.rt56.1299.el7, kernel-rt-trace 3.10.0-1160.147.1.rt56.1299.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.147.1.rt56.1299.el7
    fixed: vendor fix RHSA-2026:3634
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.107.1.rt7.448.el8_10, kernel-rt-kvm 4.18.0-553.107.1.rt7.448.el8_10, kernel-rt-core 4.18.0-553.107.1.rt7.448.el8_10, kernel-rt-modules 4.18.0-553.107.1.rt7.448.el8_10, kernel-rt-debug-kvm 4.18.0-553.107.1.rt7.448.el8_10, kernel-rt-debug-core 4.18.0-553.107.1.rt7.448.el8_10, +4 more Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.107.1.rt7.448.el8_10, kernel-rt-core 4.18.0-553.107.1.rt7.448.el8_10, kernel-rt-modules 4.18.0-553.107.1.rt7.448.el8_10, kernel-rt-debug-core 4.18.0-553.107.1.rt7.448.el8_10, kernel-rt-debug-modules 4.18.0-553.107.1.rt7.448.el8_10, kernel-rt-modules-extra 4.18.0-553.107.1.rt7.448.el8_10, +2 more
    fixed: vendor fix RHSA-2026:3110
  • Red Hat Enterprise Linux Server -EXTENSION(v. 6 ELS-EXTENSION) perf 2.6.32-754.59.1.el6, kernel 2.6.32-754.59.1.el6, kernel-kdump 2.6.32-754.59.1.el6, kernel-firmware 2.6.32-754.59.1.el6, kernel-abi-whitelists 2.6.32-754.59.1.el6, kernel-debuginfo-common-i686 2.6.32-754.59.1.el6, +2 more
    fixed: vendor fix RHSA-2026:3810
  • Red Hat Enterprise Linux Server (v. 7 ELS) perf 3.10.0-1160.147.1.el7, kernel 3.10.0-1160.147.1.el7, bpftool 3.10.0-1160.147.1.el7, python-perf 3.10.0-1160.147.1.el7, kernel-kdump 3.10.0-1160.147.1.el7, kernel-tools 3.10.0-1160.147.1.el7, +7 more
    fixed: vendor fix RHSA-2026:3685
  • Red Hat Enterprise Linux Server Optional -EXTENSION (v. 6 ELS -EXTENSION) python-perf 2.6.32-754.59.1.el6, kernel-debuginfo-common-i686 2.6.32-754.59.1.el6, kernel-debuginfo-common-s390x 2.6.32-754.59.1.el6, kernel-debuginfo-common-x86_64 2.6.32-754.59.1.el6
    fixed: vendor fix RHSA-2026:3810
  • Red Hat Enterprise Linux Server Optional (v. 7 ELS) kernel-debuginfo-common-ppc64 3.10.0-1160.147.1.el7, kernel-debuginfo-common-x86_64 3.10.0-1160.147.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-1160.147.1.el7
    fixed: vendor fix RHSA-2026:3685
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    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
total
Assessed
4 mo ago

Exploit prediction

0.19% chance of exploitation in the next 30 days, higher than 8% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CISA ADP 3.1 7.0 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 7.0 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux
  • Red Hat Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSION
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 8.2 Advanced Update Support
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.6 Telecommunications Update Service
  • Red Hat Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 9

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.