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Fencer Vulns
high 7.8

CVE-2021-47293 json

net/sched: act_skbmod: Skip non-Ethernet packets

published 2024-05-21 2 y ago modified 2026-06-17 4 mo ago also EUVD-2021-34298

cvss
7.8
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 14%
public exploits
0
none known

Summary

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

net/sched: act_skbmod: Skip non-Ethernet packets

Currently tcf_skbmod_act() assumes that packets use Ethernet as their L2 protocol, which is not always the case. As an example, for CAN devices:

$ ip link add dev vcan0 type vcan $ ip link set up vcan0 $ tc qdisc add dev vcan0 root handle 1: htb $ tc filter add dev vcan0 parent 1: protocol ip prio 10 \ matchall action skbmod swap mac

Doing the above silently corrupts all the packets. Do not perform skbmod actions for non-Ethernet packets.

Patch / fix

  • Linux Linux 4.19.199, 5.4.136, 5.10.54, 5.13.6, 5.14
  • linux Debian 14, Debian 13, Debian 12 5.14.6-1

debian advisories DEBIAN-CVE-2021-47293

  • linux Ubuntu 20.04 LTS 5.4.0-88.99
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1057.60
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1053.57
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1005.6
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1047.49
  • linux-azure Ubuntu 20.04 LTS 5.4.0-1059.62
  • linux-gkeop Ubuntu 20.04 LTS 5.4.0-1024.25
  • linux-raspi Ubuntu 20.04 LTS 5.4.0-1044.48

ubuntu advisories UBUNTU-CVE-2021-47293

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 8.6 TUS, RHEL 8.6 E4S, RHEL 8.6 AUS 4.18.0-372.111.1.el8_6
  • perf RHEL 8.6 TUS, RHEL 8.6 E4S, RHEL 8.6 AUS 4.18.0-372.111.1.el8_6
  • bpftool RHEL 8.6 TUS, RHEL 8.6 E4S, RHEL 8.6 AUS 4.18.0-372.111.1.el8_6
  • kernel-core RHEL 8.6 TUS, RHEL 8.6 E4S, RHEL 8.6 AUS 4.18.0-372.111.1.el8_6
  • kernel-tools RHEL 8.6 TUS, RHEL 8.6 E4S, RHEL 8.6 AUS 4.18.0-372.111.1.el8_6
  • python3-perf RHEL 8.6 TUS, RHEL 8.6 E4S, RHEL 8.6 AUS 4.18.0-372.111.1.el8_6
  • kernel-modules RHEL 8.6 TUS, RHEL 8.6 E4S, RHEL 8.6 AUS 4.18.0-372.111.1.el8_6
  • kernel-zfcpdump RHEL 8.6 E4S 4.18.0-372.111.1.el8_6

red hat advisories RHSA-2024:4447

  • kernel-syms SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.222.1
  • kernel-source SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.222.1
  • kernel-default SLES for SAP 12 SP5, SLES 12 SP5, SLE Workstation Extension 12 SP5 +2 more 4.12.14-122.222.1
  • kernel-obs-build SLE Software Development Kit 12 SP5 4.12.14-122.222.1
  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.191.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.191.1
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.191.1
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.191.1

suse advisories SUSE-SU-2024:2561-1SUSE-SU-2024:2381-1SUSE-SU-2024:2360-1

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-2021-47293 updated cvss 4.2

kernel: net/sched: act_skbmod: Skip non-Ethernet packets

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    affected: workaround, no fix planned “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.”
  • Red Hat Enterprise Linux BaseOS AUS (v.8.6) perf 4.18.0-372.111.1.el8_6, kernel 4.18.0-372.111.1.el8_6, bpftool 4.18.0-372.111.1.el8_6, kernel-core 4.18.0-372.111.1.el8_6, kernel-tools 4.18.0-372.111.1.el8_6, python3-perf 4.18.0-372.111.1.el8_6, +8 more Red Hat Enterprise Linux BaseOS E4S (v.8.6) perf 4.18.0-372.111.1.el8_6, kernel 4.18.0-372.111.1.el8_6, bpftool 4.18.0-372.111.1.el8_6, kernel-core 4.18.0-372.111.1.el8_6, kernel-tools 4.18.0-372.111.1.el8_6, python3-perf 4.18.0-372.111.1.el8_6, +15 more Red Hat Enterprise Linux BaseOS TUS (v.8.6) perf 4.18.0-372.111.1.el8_6, kernel 4.18.0-372.111.1.el8_6, bpftool 4.18.0-372.111.1.el8_6, kernel-core 4.18.0-372.111.1.el8_6, kernel-tools 4.18.0-372.111.1.el8_6, python3-perf 4.18.0-372.111.1.el8_6, +8 more
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2024:4447
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 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
2 y ago

Exploit prediction

0.23% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
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 Linux

Classification

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.