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Fencer Vulns
critical 9.8

CVE-2021-47013 in the critical feed json

net:emac/emac-mac: Fix a use after free in emac_mac_tx_buf_send

published 2024-02-28 2 y ago modified 2026-08-05 3 mo ago also EUVD-2021-33661

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.8%
EPSS 0.8% chance of exploitation in 30 days, percentile 56%
public exploits
0
none known

Summary

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

net:emac/emac-mac: Fix a use after free in emac_mac_tx_buf_send

In emac_mac_tx_buf_send, it calls emac_tx_fill_tpd(..,skb,..). If some error happens in emac_tx_fill_tpd(), the skb will be freed via dev_kfree_skb(skb) in error branch of emac_tx_fill_tpd(). But the freed skb is still used via skb->len by netdev_sent_queue(,skb->len).

As i observed that emac_tx_fill_tpd() haven't modified the value of skb->len, thus my patch assigns skb->len to 'len' before the possible free and use 'len' instead of skb->len later.

Patch / fix

  • Linux Linux 4.9.269, 4.14.233, 4.19.191, 5.4.119, 5.10.37, 5.11.21, 5.12.4, 5.13
  • linux Debian 14, Debian 13, Debian 12 5.10.38-1

debian advisories DEBIAN-CVE-2021-47013

  • linux Ubuntu 18.04 LTS 4.15.0-151.157
  • linux Ubuntu 20.04 LTS 5.4.0-77.86
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1109.116
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1051.53
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1046.49
  • linux-kvm Ubuntu 18.04 LTS 4.15.0-1097.99
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1041.42
  • linux-azure Ubuntu 20.04 LTS 5.4.0-1051.53

ubuntu advisories UBUNTU-CVE-2021-47013

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 4.18.0-553.5.1.rt7.346.el8_10
  • kernel-rt-kvm RHEL 8 4.18.0-553.5.1.rt7.346.el8_10
  • kernel-rt-core RHEL 8 4.18.0-553.5.1.rt7.346.el8_10
  • kernel-rt-modules RHEL 8 4.18.0-553.5.1.rt7.346.el8_10
  • kernel-rt-debug-kvm RHEL 8 4.18.0-553.5.1.rt7.346.el8_10
  • kernel-rt-debug-core RHEL 8 4.18.0-553.5.1.rt7.346.el8_10
  • kernel-rt-debug-modules RHEL 8 4.18.0-553.5.1.rt7.346.el8_10
  • kernel-rt-modules-extra RHEL 8 4.18.0-553.5.1.rt7.346.el8_10

red hat advisories RHSA-2024:3627RHSA-2024:3618RHSA-2024:3462RHSA-2024:3810

  • kernel-64kb SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS, Enterprise Storage 7.1 5.3.18-150300.59.158.1
  • kernel-syms SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.158.1
  • kernel-source SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.158.1
  • kernel-default SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +5 more 5.3.18-150300.59.158.1
  • kernel-preempt SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.158.1
  • kernel-obs-build SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.158.1
  • kernel-default-base SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +3 more 5.3.18-150300.59.158.1.150300.18.92.5
  • kernel-default SLES for SAP 15 SP2, SLES 15 SP2-LTSS, SLE Live Patching 15 SP2 +2 more 5.3.18-150200.24.188.1

suse advisories SUSE-SU-2024:1489-1SUSE-SU-2024:1454-1SUSE-SU-2024:0976-1SUSE-SU-2024:0975-1SUSE-SU-2024:0926-1SUSE-SU-2024:0925-1

  • kernel AlmaLinux 8 4.18.0-553.5.1.el8_10
  • perf AlmaLinux 8 4.18.0-553.5.1.el8_10
  • bpftool AlmaLinux 8 4.18.0-553.5.1.el8_10
  • kernel-core AlmaLinux 8 4.18.0-553.5.1.el8_10
  • kernel-tools AlmaLinux 8 4.18.0-553.5.1.el8_10
  • python3-perf AlmaLinux 8 4.18.0-553.5.1.el8_10
  • kernel-modules AlmaLinux 8 4.18.0-553.5.1.el8_10
  • kernel-zfcpdump AlmaLinux 8 4.18.0-553.5.1.el8_10

almalinux advisories ALSA-2024:3618ALSA-2024:3627

  • kernel-rt Rocky Linux 8 4.18.0-553.5.1.rt7.346.el8_10
  • kernel Rocky Linux 8 4.18.0-553.5.1.el8_10

rocky linux advisories RLSA-2024:3627RLSA-2024:3618

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-2021-47013 updated cvss 7.0

kernel: net:emac/emac-mac: Fix a use after free in emac_mac_tx_buf_send

  • 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
    affected: no fix planned “Out of support scope”
  • Red Hat CodeReady Linux Builder EUS (v.8.6) kernel-debuginfo-common-x86_64 4.18.0-372.105.1.el8_6, kernel-debuginfo-common-aarch64 4.18.0-372.105.1.el8_6, kernel-debuginfo-common-ppc64le 4.18.0-372.105.1.el8_6
    fixed: vendor fix RHSA-2024:3462
  • Red Hat CodeReady Linux Builder EUS (v.8.8) kernel-debuginfo-common-x86_64 4.18.0-477.58.1.el8_8, kernel-debuginfo-common-aarch64 4.18.0-477.58.1.el8_8, kernel-debuginfo-common-ppc64le 4.18.0-477.58.1.el8_8
    fixed: vendor fix RHSA-2024:3810
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.5.1.el8_10, kernel 4.18.0-553.5.1.el8_10, bpftool 4.18.0-553.5.1.el8_10, kernel-core 4.18.0-553.5.1.el8_10, kernel-tools 4.18.0-553.5.1.el8_10, python3-perf 4.18.0-553.5.1.el8_10, +15 more
    fixed: vendor fix RHSA-2024:3618
  • Red Hat Enterprise Linux BaseOS EUS (v.8.6) perf 4.18.0-372.105.1.el8_6, kernel 4.18.0-372.105.1.el8_6, bpftool 4.18.0-372.105.1.el8_6, kernel-core 4.18.0-372.105.1.el8_6, kernel-tools 4.18.0-372.105.1.el8_6, python3-perf 4.18.0-372.105.1.el8_6, +15 more
    fixed: vendor fix RHSA-2024:3462
  • Red Hat Enterprise Linux BaseOS EUS (v.8.8) perf 4.18.0-477.58.1.el8_8, kernel 4.18.0-477.58.1.el8_8, bpftool 4.18.0-477.58.1.el8_8, kernel-core 4.18.0-477.58.1.el8_8, kernel-tools 4.18.0-477.58.1.el8_8, python3-perf 4.18.0-477.58.1.el8_8, +15 more
    fixed: vendor fix RHSA-2024:3810
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.5.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.5.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.5.1.el8_10
    fixed: vendor fix RHSA-2024:3618
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.5.1.rt7.346.el8_10, kernel-rt-kvm 4.18.0-553.5.1.rt7.346.el8_10, kernel-rt-core 4.18.0-553.5.1.rt7.346.el8_10, kernel-rt-modules 4.18.0-553.5.1.rt7.346.el8_10, kernel-rt-debug-kvm 4.18.0-553.5.1.rt7.346.el8_10, kernel-rt-debug-core 4.18.0-553.5.1.rt7.346.el8_10, +4 more Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.5.1.rt7.346.el8_10, kernel-rt-core 4.18.0-553.5.1.rt7.346.el8_10, kernel-rt-modules 4.18.0-553.5.1.rt7.346.el8_10, kernel-rt-debug-core 4.18.0-553.5.1.rt7.346.el8_10, kernel-rt-debug-modules 4.18.0-553.5.1.rt7.346.el8_10, kernel-rt-modules-extra 4.18.0-553.5.1.rt7.346.el8_10, +2 more
    fixed: vendor fix RHSA-2024:3627
show 2 more
  • Red Hat Virtualization 4 Hypervisor for RHEL 8 perf 4.18.0-372.105.1.el8_6, kernel-debuginfo-common-x86_64 4.18.0-372.105.1.el8_6
    fixed: vendor fix RHSA-2024:3462
  • 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

0.79% chance of exploitation in the next 30 days, higher than 56% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/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 Linux

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.