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Fencer Vulns
high 7.8

CVE-2023-4206 json

Use-after-free in Linux kernel's net/sched: cls_route component

published 2023-09-06 3 y ago modified 2026-06-17 4 mo ago also EUVD-2023-54080

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits
0
none known

Summary

A use-after-free vulnerability in the Linux kernel's net/sched: cls_route component can be exploited to achieve local privilege escalation.

When route4_change() is called on an existing filter, the whole tcf_result struct is always copied into the new instance of the filter. This causes a problem when updating a filter bound to a class, as tcf_unbind_filter() is always called on the old instance in the success path, decreasing filter_cnt of the still referenced class and allowing it to be deleted, leading to a use-after-free.

We recommend upgrading past commit b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8.

Patch / fix

  • Linux Kernel 6.5
  • linux Debian 12 6.1.52-1
  • linux Debian 14, Debian 13 6.4.11-1

debian advisories DEBIAN-CVE-2023-4206

  • linux Ubuntu 20.04 LTS 5.4.0-163.180
  • linux Ubuntu 22.04 LTS 5.15.0-84.93
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1110.119
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1045.50
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1113.122
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1042.50
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1042.47
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1057.62

ubuntu advisories UBUNTU-CVE-2023-4206

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 4.18.0-513.5.1.el8_9
  • perf RHEL 8 4.18.0-513.5.1.el8_9
  • bpftool RHEL 8 4.18.0-513.5.1.el8_9
  • kernel-core RHEL 8 4.18.0-513.5.1.el8_9
  • kernel-tools RHEL 8 4.18.0-513.5.1.el8_9
  • python3-perf RHEL 8 4.18.0-513.5.1.el8_9
  • kernel-modules RHEL 8 4.18.0-513.5.1.el8_9
  • kernel-zfcpdump RHEL 8 4.18.0-513.5.1.el8_9

red hat advisories RHSA-2023:7539RHSA-2023:7370RHSA-2023:7379RHSA-2023:7077RHSA-2023:6583RHSA-2023:6901

  • kernel AlmaLinux 8 4.18.0-513.5.1.el8_9
  • perf AlmaLinux 8 4.18.0-513.5.1.el8_9
  • bpftool AlmaLinux 8 4.18.0-513.5.1.el8_9
  • kernel-core AlmaLinux 8 4.18.0-513.5.1.el8_9
  • kernel-tools AlmaLinux 8 4.18.0-513.5.1.el8_9
  • python3-perf AlmaLinux 8 4.18.0-513.5.1.el8_9
  • kernel-modules AlmaLinux 8 4.18.0-513.5.1.el8_9
  • kernel-zfcpdump AlmaLinux 8 4.18.0-513.5.1.el8_9

almalinux advisories ALSA-2023:7077

  • kernel CBL-Mariner 2.0 5.15.131.1-2

azure linux advisories AZL-28674

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-2023-4206 updated cvss 7.8

kernel: net/sched: Use-after-free vulnerabilities in the net/sched classifiers: cls_fw, cls_u32 and cls_route

  • 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: workaround, no fix available “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~”
  • Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-513.5.1.el8_9, kernel-debuginfo-common-aarch64 4.18.0-513.5.1.el8_9, kernel-debuginfo-common-ppc64le 4.18.0-513.5.1.el8_9
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7077
  • Red Hat CodeReady Linux Builder (v. 9) libperf 5.14.0-362.8.1.el9_3, kernel-debuginfo-common-s390x 5.14.0-362.8.1.el9_3, kernel-debuginfo-common-x86_64 5.14.0-362.8.1.el9_3, kernel-debuginfo-common-aarch64 5.14.0-362.8.1.el9_3, kernel-debuginfo-common-ppc64le 5.14.0-362.8.1.el9_3
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:6583
  • Red Hat CodeReady Linux Builder EUS (v.8.8) kernel-debuginfo-common-x86_64 4.18.0-477.36.1.el8_8, kernel-debuginfo-common-aarch64 4.18.0-477.36.1.el8_8, kernel-debuginfo-common-ppc64le 4.18.0-477.36.1.el8_8
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7539
  • Red Hat CodeReady Linux Builder EUS (v.9.2) kernel-debuginfo-common-s390x 5.14.0-284.40.1.el9_2, kernel-debuginfo-common-x86_64 5.14.0-284.40.1.el9_2, kernel-debuginfo-common-aarch64 5.14.0-284.40.1.el9_2, kernel-debuginfo-common-ppc64le 5.14.0-284.40.1.el9_2
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7370
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-362.8.1.el9_3, perf 5.14.0-362.8.1.el9_3, rtla 5.14.0-362.8.1.el9_3, kernel-devel-matched 5.14.0-362.8.1.el9_3, kernel-64k-devel-matched 5.14.0-362.8.1.el9_3, kernel-debug-devel-matched 5.14.0-362.8.1.el9_3, +6 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:6583
  • Red Hat Enterprise Linux AppStream EUS (v.9.2) perf 5.14.0-284.40.1.el9_2, rtla 5.14.0-284.40.1.el9_2, kernel-devel-matched 5.14.0-284.40.1.el9_2, kernel-64k-devel-matched 5.14.0-284.40.1.el9_2, kernel-debug-devel-matched 5.14.0-284.40.1.el9_2, kernel-debuginfo-common-s390x 5.14.0-284.40.1.el9_2, +5 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7370
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-513.5.1.el8_9, kernel 4.18.0-513.5.1.el8_9, bpftool 4.18.0-513.5.1.el8_9, kernel-core 4.18.0-513.5.1.el8_9, kernel-tools 4.18.0-513.5.1.el8_9, python3-perf 4.18.0-513.5.1.el8_9, +15 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7077
show 19 more
  • Red Hat Enterprise Linux BaseOS (v. 9) bpftool 7.2.0-362.8.1.el9_3, kernel 5.14.0-362.8.1.el9_3, kernel-64k 5.14.0-362.8.1.el9_3, kernel-core 5.14.0-362.8.1.el9_3, kernel-tools 5.14.0-362.8.1.el9_3, python3-perf 5.14.0-362.8.1.el9_3, +28 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:6583
  • Red Hat Enterprise Linux BaseOS EUS (v.8.8) perf 4.18.0-477.36.1.el8_8, kernel 4.18.0-477.36.1.el8_8, bpftool 4.18.0-477.36.1.el8_8, kernel-core 4.18.0-477.36.1.el8_8, kernel-tools 4.18.0-477.36.1.el8_8, python3-perf 4.18.0-477.36.1.el8_8, +20 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7539
  • Red Hat Enterprise Linux BaseOS EUS (v.9.2) bpftool 7.0.0-284.40.1.el9_2, kernel 5.14.0-284.40.1.el9_2, kernel-64k 5.14.0-284.40.1.el9_2, kernel-core 5.14.0-284.40.1.el9_2, kernel-tools 5.14.0-284.40.1.el9_2, python3-perf 5.14.0-284.40.1.el9_2, +32 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7370
  • Red Hat Enterprise Linux Client (v. 7) perf 3.10.0-1160.105.1.el7, kernel 3.10.0-1160.105.1.el7, bpftool 3.10.0-1160.105.1.el7, python-perf 3.10.0-1160.105.1.el7, kernel-tools 3.10.0-1160.105.1.el7, kernel-tools-libs 3.10.0-1160.105.1.el7, +2 more Red Hat Enterprise Linux Client Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.105.1.el7 Red Hat Enterprise Linux ComputeNode Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.105.1.el7
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7423
  • Red Hat Enterprise Linux for Real Time (v. 7) kernel-rt 3.10.0-1160.105.1.rt56.1256.el7, kernel-rt-trace 3.10.0-1160.105.1.rt56.1256.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.105.1.rt56.1256.el7 Red Hat Enterprise Linux for Real Time for NFV (v. 7) kernel-rt 3.10.0-1160.105.1.rt56.1256.el7, kernel-rt-kvm 3.10.0-1160.105.1.rt56.1256.el7, kernel-rt-trace 3.10.0-1160.105.1.rt56.1256.el7, kernel-rt-debug-kvm 3.10.0-1160.105.1.rt56.1256.el7, kernel-rt-trace-kvm 3.10.0-1160.105.1.rt56.1256.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.105.1.rt56.1256.el7
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7424
  • Red Hat Enterprise Linux Real Time (v. 8) kernel-rt 4.18.0-513.5.1.rt7.307.el8_9, kernel-rt-core 4.18.0-513.5.1.rt7.307.el8_9, kernel-rt-modules 4.18.0-513.5.1.rt7.307.el8_9, kernel-rt-debug-core 4.18.0-513.5.1.rt7.307.el8_9, kernel-rt-debug-modules 4.18.0-513.5.1.rt7.307.el8_9, kernel-rt-modules-extra 4.18.0-513.5.1.rt7.307.el8_9, +2 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:6901
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-362.8.1.el9_3, kernel-rt-core 5.14.0-362.8.1.el9_3, kernel-rt-modules 5.14.0-362.8.1.el9_3, kernel-rt-debug-core 5.14.0-362.8.1.el9_3, kernel-rt-modules-core 5.14.0-362.8.1.el9_3, kernel-rt-debug-modules 5.14.0-362.8.1.el9_3, +4 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:6583
  • Red Hat Enterprise Linux Real Time EUS (v.9.2) kernel-rt 5.14.0-284.40.1.rt14.325.el9_2, kernel-rt-core 5.14.0-284.40.1.rt14.325.el9_2, kernel-rt-modules 5.14.0-284.40.1.rt14.325.el9_2, kernel-rt-debug-core 5.14.0-284.40.1.rt14.325.el9_2, kernel-rt-modules-core 5.14.0-284.40.1.rt14.325.el9_2, kernel-rt-debug-modules 5.14.0-284.40.1.rt14.325.el9_2, +4 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7379
  • Red Hat Enterprise Linux Real Time for NFV (v. 8) kernel-rt 4.18.0-513.5.1.rt7.307.el8_9, kernel-rt-kvm 4.18.0-513.5.1.rt7.307.el8_9, kernel-rt-core 4.18.0-513.5.1.rt7.307.el8_9, kernel-rt-modules 4.18.0-513.5.1.rt7.307.el8_9, kernel-rt-debug-kvm 4.18.0-513.5.1.rt7.307.el8_9, kernel-rt-debug-core 4.18.0-513.5.1.rt7.307.el8_9, +4 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:6901
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-362.8.1.el9_3, kernel-rt-kvm 5.14.0-362.8.1.el9_3, kernel-rt-core 5.14.0-362.8.1.el9_3, kernel-rt-modules 5.14.0-362.8.1.el9_3, kernel-rt-debug-kvm 5.14.0-362.8.1.el9_3, kernel-rt-debug-core 5.14.0-362.8.1.el9_3, +6 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:6583
  • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.2) kernel-rt 5.14.0-284.40.1.rt14.325.el9_2, kernel-rt-kvm 5.14.0-284.40.1.rt14.325.el9_2, kernel-rt-core 5.14.0-284.40.1.rt14.325.el9_2, kernel-rt-modules 5.14.0-284.40.1.rt14.325.el9_2, kernel-rt-debug-kvm 5.14.0-284.40.1.rt14.325.el9_2, kernel-rt-debug-core 5.14.0-284.40.1.rt14.325.el9_2, +6 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7379
  • Red Hat Enterprise Linux Server (v. 7) perf 3.10.0-1160.105.1.el7, kernel 3.10.0-1160.105.1.el7, bpftool 3.10.0-1160.105.1.el7, python-perf 3.10.0-1160.105.1.el7, kernel-kdump 3.10.0-1160.105.1.el7, kernel-tools 3.10.0-1160.105.1.el7, +12 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7423
  • Red Hat Enterprise Linux Server AUS (v. 7.6) perf 3.10.0-957.109.1.el7, kernel 3.10.0-957.109.1.el7, bpftool 3.10.0-957.109.1.el7, python-perf 3.10.0-957.109.1.el7, kernel-tools 3.10.0-957.109.1.el7, kernel-tools-libs 3.10.0-957.109.1.el7, +2 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2024:0261
  • Red Hat Enterprise Linux Server AUS (v. 7.7) perf 3.10.0-1062.82.1.el7, kernel 3.10.0-1062.82.1.el7, bpftool 3.10.0-1062.82.1.el7, python-perf 3.10.0-1062.82.1.el7, kernel-tools 3.10.0-1062.82.1.el7, kernel-tools-libs 3.10.0-1062.82.1.el7, +2 more
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2024:0262
  • Red Hat Enterprise Linux Server Optional (v. 7) kernel-debuginfo-common-ppc64 3.10.0-1160.105.1.el7, kernel-debuginfo-common-x86_64 3.10.0-1160.105.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-1160.105.1.el7
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7423
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.6) kernel-debuginfo-common-x86_64 3.10.0-957.109.1.el7
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2024:0261
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.7) kernel-debuginfo-common-x86_64 3.10.0-1062.82.1.el7
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2024:0262
  • Red Hat Enterprise Linux Workstation (v. 7) perf 3.10.0-1160.105.1.el7, kernel 3.10.0-1160.105.1.el7, bpftool 3.10.0-1160.105.1.el7, python-perf 3.10.0-1160.105.1.el7, kernel-tools 3.10.0-1160.105.1.el7, kernel-tools-libs 3.10.0-1160.105.1.el7, +2 more Red Hat Enterprise Linux Workstation Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.105.1.el7
    fixed: vendor fix “To mitigate this issue, prevent the module cls_u32 from being loaded by blacklisting the module to prevent it from loading automatically. ~~~ https://access.redhat.com/solutions/41278 ~~~” RHSA-2023:7423
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux AppStream EUS (v.9.2) kernel-doc 5.14.0-284.40.1.el9_2
    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

Exploit prediction

0.59% chance of exploitation in the next 30 days, higher than 48% 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
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Kernel

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.