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Fencer Intel
high 7.1

CVE-2021-3752 json

A use-after-free flaw was found in the Linux kernel’s Bluetooth subsystem in the way user calls connect to the socket and disconnect simult…

published 4y ago modified 4mo ago also EUVD-2021-27027

cvss
7.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.7%
EPSS 1.7% chance of exploitation in 30 days, percentile 77%
public exploits
0
none known

Summary

A use-after-free flaw was found in the Linux kernel’s Bluetooth subsystem in the way user calls connect to the socket and disconnect simultaneously due to a race condition. This flaw allows a user to crash the system or escalate their privileges. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.

Patch / fix

  • linux linux_kernel 4.4.293, 4.9.291, 4.14.256, 4.19.218, 5.4.160, 5.10.80, 5.14.19, 5.15.3
  • linux Debian 14, Debian 13, Debian 12 5.15.3-1

debian advisories DEBIAN-CVE-2021-3752

  • linux Ubuntu 18.04 LTS 4.15.0-167.175
  • linux Ubuntu 20.04 LTS 5.4.0-97.110
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1119.127
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1064.67
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1063.67
  • linux-gke Ubuntu 20.04 LTS 5.4.0-1061.64
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1013.14
  • linux-kvm Ubuntu 18.04 LTS 4.15.0-1106.108

ubuntu advisories UBUNTU-CVE-2021-3752

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 4.18.0-372.9.1.el8
  • perf RHEL 8 4.18.0-372.9.1.el8
  • bpftool RHEL 8 4.18.0-372.9.1.el8
  • kernel-core RHEL 8 4.18.0-372.9.1.el8
  • kernel-tools RHEL 8 4.18.0-372.9.1.el8
  • python3-perf RHEL 8 4.18.0-372.9.1.el8
  • kernel-modules RHEL 8 4.18.0-372.9.1.el8
  • kernel-zfcpdump RHEL 8 4.18.0-372.9.1.el8

red hat advisories RHSA-2022:1988RHSA-2022:0622RHSA-2022:0620RHSA-2022:1975

  • kernel-syms SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.12.14-95.83.2
  • kernel-source SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.12.14-95.83.2
  • kernel-default SLES for SAP 12 SP4, SLES 12 SP4-LTSS, SLE Live Patching 12 SP4 +3 more 4.12.14-95.83.2
  • kernel-syms SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.78.1
  • kernel-source SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.78.1
  • kernel-default SLES for SAP 15, SLES 15-LTSS, SLE Live Patching 15 +3 more 4.12.14-150.78.1
  • kernel-vanilla SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.78.1
  • kernel-obs-build SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.78.2

suse advisories SUSE-SU-2021:3972-1SUSE-SU-2021:3969-1SUSE-SU-2021:3935-1SUSE-SU-2021:3929-1SUSE-SU-2021:3876-1SUSE-SU-2021:3751-1

  • kernel-default openSUSE Leap 15.3 4.12.14-197.102.2
  • kernel-vanilla openSUSE Leap 15.3 4.12.14-197.102.2
  • kernel-kvmsmall openSUSE Leap 15.3 4.12.14-197.102.2
  • kernel-zfcpdump openSUSE Leap 15.3 4.12.14-197.102.2
  • kmod openSUSE Leap 15.2 25-lp152.8.3.1
  • kmod-testsuite openSUSE Leap 15.2 25-lp152.8.3.2
  • kernel-syms openSUSE Leap 15.2 5.3.18-lp152.95.1
  • kernel-obs-qa openSUSE Leap 15.2 5.3.18-lp152.95.1

opensuse advisories openSUSE-SU-2021:3876-1openSUSE-SU-2021:1365-1openSUSE-SU-2021:1357-1openSUSE-SU-2021:3447-1openSUSE-SU-2021:3387-1openSUSE-SU-2021:3338-1

  • kernel AlmaLinux 8 4.18.0-372.9.1.el8
  • perf AlmaLinux 8 4.18.0-372.9.1.el8
  • bpftool AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-core AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-tools AlmaLinux 8 4.18.0-372.9.1.el8
  • python3-perf AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-modules AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-debug-core AlmaLinux 8 4.18.0-372.9.1.el8

almalinux advisories ALSA-2022:1988

  • kernel Rocky Linux 8 4.18.0-372.9.1.el8
  • kernel-rt Rocky Linux 8 4.18.0-372.9.1.rt7.166.el8

rocky linux advisories RLSA-2022:1988RLSA-2022:1975

  • linux-lts Arch Linux 5.15.2-1

arch linux advisories AVG-1741

Is CVE-2021-3752 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2021-3752 updated cvss 7.0

kernel: possible use-after-free in bluetooth module

  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-372.9.1.el8, kernel 4.18.0-372.9.1.el8, bpftool 4.18.0-372.9.1.el8, kernel-core 4.18.0-372.9.1.el8, kernel-tools 4.18.0-372.9.1.el8, python3-perf 4.18.0-372.9.1.el8, +15 more
    fixed: vendor fix RHSA-2022:1988
  • Red Hat Enterprise Linux Client (v. 7) perf 3.10.0-1160.59.1.el7, kernel 3.10.0-1160.59.1.el7, bpftool 3.10.0-1160.59.1.el7, python-perf 3.10.0-1160.59.1.el7, kernel-tools 3.10.0-1160.59.1.el7, kernel-tools-libs 3.10.0-1160.59.1.el7, +2 more Red Hat Enterprise Linux Client Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.59.1.el7 Red Hat Enterprise Linux ComputeNode Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.59.1.el7
    fixed: vendor fix RHSA-2022:0620
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-372.9.1.el8, kernel-debuginfo-common-aarch64 4.18.0-372.9.1.el8, kernel-debuginfo-common-ppc64le 4.18.0-372.9.1.el8
    fixed: vendor fix RHSA-2022:1988
  • Red Hat Enterprise Linux for Real Time (v. 7) kernel-rt 3.10.0-1160.59.1.rt56.1200.el7, kernel-rt-trace 3.10.0-1160.59.1.rt56.1200.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.59.1.rt56.1200.el7 Red Hat Enterprise Linux for Real Time for NFV (v. 7) kernel-rt 3.10.0-1160.59.1.rt56.1200.el7, kernel-rt-kvm 3.10.0-1160.59.1.rt56.1200.el7, kernel-rt-trace 3.10.0-1160.59.1.rt56.1200.el7, kernel-rt-debug-kvm 3.10.0-1160.59.1.rt56.1200.el7, kernel-rt-trace-kvm 3.10.0-1160.59.1.rt56.1200.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.59.1.rt56.1200.el7
    fixed: vendor fix RHSA-2022:0622
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-372.9.1.rt7.166.el8, kernel-rt-kvm 4.18.0-372.9.1.rt7.166.el8, kernel-rt-core 4.18.0-372.9.1.rt7.166.el8, kernel-rt-modules 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-kvm 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-core 4.18.0-372.9.1.rt7.166.el8, +4 more Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-372.9.1.rt7.166.el8, kernel-rt-core 4.18.0-372.9.1.rt7.166.el8, kernel-rt-modules 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-core 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-modules 4.18.0-372.9.1.rt7.166.el8, kernel-rt-modules-extra 4.18.0-372.9.1.rt7.166.el8, +2 more
    fixed: vendor fix RHSA-2022:1975
  • Red Hat Enterprise Linux Server (v. 7) perf 3.10.0-1160.59.1.el7, kernel 3.10.0-1160.59.1.el7, bpftool 3.10.0-1160.59.1.el7, python-perf 3.10.0-1160.59.1.el7, kernel-kdump 3.10.0-1160.59.1.el7, kernel-tools 3.10.0-1160.59.1.el7, +7 more Red Hat Enterprise Linux Server Optional (v. 7) kernel-debuginfo-common-ppc64 3.10.0-1160.59.1.el7, kernel-debuginfo-common-x86_64 3.10.0-1160.59.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-1160.59.1.el7 Red Hat Enterprise Linux Workstation (v. 7) perf 3.10.0-1160.59.1.el7, kernel 3.10.0-1160.59.1.el7, bpftool 3.10.0-1160.59.1.el7, python-perf 3.10.0-1160.59.1.el7, kernel-tools 3.10.0-1160.59.1.el7, kernel-tools-libs 3.10.0-1160.59.1.el7, +2 more Red Hat Enterprise Linux Workstation Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.59.1.el7
    fixed: vendor fix RHSA-2022:0620
  • Red Hat Enterprise Linux 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 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

Exploit prediction

1.74% chance of exploitation in the next 30 days, higher than 77% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • openwall.com https://www.openwall.com/lists/oss-security/2021/09/15/4 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 7.1 CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.9 AV:A/AC:M/Au:N/C:C/I:C/A:C

Affected products

  • n/a kernel

Classification

Weakness
  • CWE-416 Use After Free
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
Technology feeds

References

Sources

Fencer Intel 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.