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Fencer Vulns
critical 9.8

CVE-2021-47232 in the critical feed json

can: j1939: fix Use-after-Free, hold skb ref while in use

published 2024-05-21 2 y ago modified 2026-08-05 3 mo ago also EUVD-2021-33880

cvss
9.8
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 50%
public exploits
0
none known

Summary

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

can: j1939: fix Use-after-Free, hold skb ref while in use

This patch fixes a Use-after-Free found by the syzbot.

The problem is that a skb is taken from the per-session skb queue, without incrementing the ref count. This leads to a Use-after-Free if the skb is taken concurrently from the session queue due to a CTS.

Patch / fix

  • Linux Linux 5.4.128, 5.10.46, 5.12.13, 5.13
  • linux linux_kernel 22cba878abf6, 509ab6bfdd0c, 1071065eeb33, 2030043e616c
  • linux Debian 14, Debian 13, Debian 12 5.10.46-1

debian advisories DEBIAN-CVE-2021-47232

  • linux Ubuntu 20.04 LTS 5.4.0-81.91
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1055.58
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1051.55
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1045.47
  • linux-azure Ubuntu 20.04 LTS 5.4.0-1056.58
  • linux-gkeop Ubuntu 20.04 LTS 5.4.0-1022.23
  • linux-raspi Ubuntu 20.04 LTS 5.4.0-1042.46
  • linux-oracle Ubuntu 20.04 LTS 5.4.0-1053.57

ubuntu advisories UBUNTU-CVE-2021-47232

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

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-2021-47232 updated cvss 5.5

kernel: can: j1939: fix Use-after-Free, hold skb ref while in use

  • Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-selftests-internal
    affected: no fix available
  • 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 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, +82 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
total
Assessed
2 y ago

Exploit prediction

0.62% chance of exploitation in the next 30 days, higher than 50% 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
CISA ADP 3.1 8.4 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 8.4 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux
  • linux 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.