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Fencer Vulns
high 7.7

CVE-2021-47356 json

mISDN: fix possible use-after-free in HFC_cleanup()

published 2024-05-21 2 y ago modified 2026-06-17 4 mo ago also EUVD-2021-34361

cvss
7.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 18%
public exploits
0
none known

Summary

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

mISDN: fix possible use-after-free in HFC_cleanup()

This module's remove path calls del_timer(). However, that function does not wait until the timer handler finishes. This means that the timer handler may still be running after the driver's remove function has finished, which would result in a use-after-free.

Fix by calling del_timer_sync(), which makes sure the timer handler has finished, and unable to re-schedule itself.

Patch / fix

  • Linux Linux 4.4.276, 4.9.276, 4.14.240, 4.19.198, 5.4.133, 5.10.51, 5.12.18, 5.13.3, 5.14
  • linux linux_kernel 3ecd228c636e, 5f2818185da0, 009fc857c5f6, 54ff32029289, 7867ddc5f3de, 49331c07ef0f, 61370ff07e0a, b7ee9ae1e0cf, ed7c3739d0a0
  • linux Debian 14, Debian 13, Debian 12 5.14.6-1

debian advisories DEBIAN-CVE-2021-47356

  • linux Ubuntu 18.04 LTS 4.15.0-156.163
  • linux Ubuntu 20.04 LTS 5.4.0-84.94
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1111.118
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1056.59
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1052.56
  • linux-kvm Ubuntu 18.04 LTS 4.15.0-1099.101
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1046.48
  • linux-azure Ubuntu 20.04 LTS 5.4.0-1058.60

ubuntu advisories UBUNTU-CVE-2021-47356

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 4.18.0-553.8.1.el8_10
  • perf RHEL 8 4.18.0-553.8.1.el8_10
  • bpftool RHEL 8 4.18.0-553.8.1.el8_10
  • kernel-core RHEL 8 4.18.0-553.8.1.el8_10
  • kernel-tools RHEL 8 4.18.0-553.8.1.el8_10
  • python3-perf RHEL 8 4.18.0-553.8.1.el8_10
  • kernel-modules RHEL 8 4.18.0-553.8.1.el8_10
  • kernel-zfcpdump RHEL 8 4.18.0-553.8.1.el8_10

red hat advisories RHSA-2024:6993RHSA-2024:4211RHSA-2024:5692RHSA-2024:4352

  • kernel-64kb SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS, Enterprise Storage 7.1 5.3.18-150300.59.164.1
  • kernel-syms SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-source SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-default SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +5 more 5.3.18-150300.59.164.1
  • kernel-preempt SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-obs-build SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-default-base SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +3 more 5.3.18-150300.59.164.1.150300.18.96.1
  • kernel-syms SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.219.1

suse advisories SUSE-SU-2024:2185-1SUSE-SU-2024:2184-1SUSE-SU-2024:2183-1SUSE-SU-2024:2010-1SUSE-SU-2024:1983-1SUSE-SU-2024:1979-1

  • kernel-rt AlmaLinux 8 4.18.0-553.8.1.rt7.349.el8_10
  • kernel-rt-kvm AlmaLinux 8 4.18.0-553.8.1.rt7.349.el8_10
  • kernel-rt-core AlmaLinux 8 4.18.0-553.8.1.rt7.349.el8_10
  • kernel-rt-modules AlmaLinux 8 4.18.0-553.8.1.rt7.349.el8_10
  • kernel-rt-debug-kvm AlmaLinux 8 4.18.0-553.8.1.rt7.349.el8_10
  • kernel-rt-debug-core AlmaLinux 8 4.18.0-553.8.1.rt7.349.el8_10
  • kernel-rt-debug-modules AlmaLinux 8 4.18.0-553.8.1.rt7.349.el8_10
  • kernel-rt-modules-extra AlmaLinux 8 4.18.0-553.8.1.rt7.349.el8_10

almalinux advisories ALSA-2024:4352ALSA-2024:4211

  • kernel-rt Rocky Linux 8 4.18.0-553.8.1.rt7.349.el8_10
  • kernel Rocky Linux 8 4.18.0-553.8.1.el8_10

rocky linux advisories RLSA-2024:4352RLSA-2024:4211

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-2021-47356 updated cvss 6.7

kernel: mISDN: fix possible use-after-free in HFC_cleanup()

  • 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: 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 CodeReady Linux Builder EUS (v.8.8) kernel-debuginfo-common-x86_64 4.18.0-477.74.1.el8_8, kernel-debuginfo-common-aarch64 4.18.0-477.74.1.el8_8, kernel-debuginfo-common-ppc64le 4.18.0-477.74.1.el8_8
    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-2024:6993
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.8.1.el8_10, kernel 4.18.0-553.8.1.el8_10, bpftool 4.18.0-553.8.1.el8_10, kernel-core 4.18.0-553.8.1.el8_10, kernel-tools 4.18.0-553.8.1.el8_10, python3-perf 4.18.0-553.8.1.el8_10, +15 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-2024:4211
  • Red Hat Enterprise Linux BaseOS AUS (v.8.6) perf 4.18.0-372.119.1.el8_6, kernel 4.18.0-372.119.1.el8_6, bpftool 4.18.0-372.119.1.el8_6, kernel-core 4.18.0-372.119.1.el8_6, kernel-tools 4.18.0-372.119.1.el8_6, python3-perf 4.18.0-372.119.1.el8_6, +8 more Red Hat Enterprise Linux BaseOS E4S (v.8.6) perf 4.18.0-372.119.1.el8_6, kernel 4.18.0-372.119.1.el8_6, bpftool 4.18.0-372.119.1.el8_6, kernel-core 4.18.0-372.119.1.el8_6, kernel-tools 4.18.0-372.119.1.el8_6, python3-perf 4.18.0-372.119.1.el8_6, +15 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-2024:5692
  • Red Hat Enterprise Linux BaseOS EUS (v.8.8) perf 4.18.0-477.74.1.el8_8, kernel 4.18.0-477.74.1.el8_8, bpftool 4.18.0-477.74.1.el8_8, kernel-core 4.18.0-477.74.1.el8_8, kernel-tools 4.18.0-477.74.1.el8_8, python3-perf 4.18.0-477.74.1.el8_8, +15 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-2024:6993
  • Red Hat Enterprise Linux BaseOS TUS (v.8.6) perf 4.18.0-372.119.1.el8_6, kernel 4.18.0-372.119.1.el8_6, bpftool 4.18.0-372.119.1.el8_6, kernel-core 4.18.0-372.119.1.el8_6, kernel-tools 4.18.0-372.119.1.el8_6, python3-perf 4.18.0-372.119.1.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-2024:5692
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.8.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.8.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.8.1.el8_10
    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-2024:4211
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.8.1.rt7.349.el8_10, kernel-rt-kvm 4.18.0-553.8.1.rt7.349.el8_10, kernel-rt-core 4.18.0-553.8.1.rt7.349.el8_10, kernel-rt-modules 4.18.0-553.8.1.rt7.349.el8_10, kernel-rt-debug-kvm 4.18.0-553.8.1.rt7.349.el8_10, kernel-rt-debug-core 4.18.0-553.8.1.rt7.349.el8_10, +4 more Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.8.1.rt7.349.el8_10, kernel-rt-core 4.18.0-553.8.1.rt7.349.el8_10, kernel-rt-modules 4.18.0-553.8.1.rt7.349.el8_10, kernel-rt-debug-core 4.18.0-553.8.1.rt7.349.el8_10, kernel-rt-debug-modules 4.18.0-553.8.1.rt7.349.el8_10, kernel-rt-modules-extra 4.18.0-553.8.1.rt7.349.el8_10, +2 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-2024:4352
show 1 more
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux BaseOS (v. 8) kernel-headers 4.18.0-553.8.1.el8_10, kernel-cross-headers 4.18.0-553.8.1.el8_10 Red Hat Enterprise Linux BaseOS AUS (v.8.6) kernel-doc 4.18.0-372.119.1.el8_6 Red Hat Enterprise Linux BaseOS E4S (v.8.6) kernel-doc 4.18.0-372.119.1.el8_6 Red Hat Enterprise Linux BaseOS TUS (v.8.6) kernel-doc 4.18.0-372.119.1.el8_6
    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
21 mo ago

Exploit prediction

0.27% chance of exploitation in the next 30 days, higher than 18% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.7 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
CNA 3.1 7.7 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/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.