Skip to content
Fencer Vulns
high 7.5

CVE-2021-34981 json

Linux Kernel Bluetooth CMTP Module Double Free Privilege Escalation Vulnerability

published 2024-05-07 2 y ago modified 2026-06-17 4 mo ago also EUVD-2021-21628

cvss
7.5
version 3.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 9%
public exploits
0
none known

Summary

Linux Kernel Bluetooth CMTP Module Double Free Privilege Escalation Vulnerability. This vulnerability allows local attackers to escalate privileges on affected installations of Linux Kernel. An attacker must first obtain the ability to execute high-privileged code on the target system in order to exploit this vulnerability.

The specific flaw exists within the CMTP module. The issue results from the lack of validating the existence of an object prior to performing further free operations on the object. An attacker can leverage this vulnerability to escalate privileges and execute code in the context of the kernel. Was ZDI-CAN-11977.

Patch / fix

  • linux linux_kernel 5.10.42
  • linux Debian 14, Debian 13, Debian 12 5.10.46-1

debian advisories DEBIAN-CVE-2021-34981

  • linux-oem-5.13 Ubuntu 20.04 LTS 5.13.0-1014.18

ubuntu advisories UBUNTU-CVE-2021-34981

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 SLE Real Time 12 SP5 4.12.14-10.70.2
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.70.2
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.70.2
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.70.2
  • kernel-rt SLE Micro 5.1, Real Time Module 15 SP3 5.3.18-65.2
  • kernel-syms-rt Real Time Module 15 SP3 5.3.18-65.1
  • kernel-rt_debug Real Time Module 15 SP3 5.3.18-65.2
  • kernel-source-rt Real Time Module 15 SP3 5.3.18-65.2

suse advisories SUSE-SU-2023:0416-1SUSE-SU-2021:3992-1SUSE-SU-2021:3979-1SUSE-SU-2021:3978-1SUSE-SU-2021:3972-1SUSE-SU-2021:3969-1

  • dtb-aarch64 openSUSE Leap 15.3 5.3.18-59.37.1
  • kernel-64kb openSUSE Leap 15.3 5.3.18-59.37.2
  • kernel-syms openSUSE Leap 15.3 5.3.18-59.37.1
  • kernel-obs-qa openSUSE Leap 15.3 5.3.18-59.37.1
  • kernel-source openSUSE Leap 15.3 5.3.18-59.37.2
  • kernel-default openSUSE Leap 15.3 5.3.18-59.37.2
  • kernel-preempt openSUSE Leap 15.3 5.3.18-59.37.2
  • kernel-kvmsmall openSUSE Leap 15.3 5.3.18-59.37.2

opensuse advisories openSUSE-SU-2021:3941-1openSUSE-SU-2021:3876-1openSUSE-SU-2021:3806-1openSUSE-SU-2021:1501-1

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-2021-34981 updated cvss 7.5

kernel: Bluetooth CMTP Module Double Free Privilege Escalation Vulnerability

  • 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 “Out of support scope”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +81 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

0.20% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.0 7.5 CVSS:3.0/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
NVD 3.1 6.7 CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Affected products

  • 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.