CVE-2021-34981
kernel: Bluetooth CMTP Module Double Free Privilege Escalation Vulnerability
Severity
ModerateRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · October 25, 2021
Updated · November 21, 2025
Description
A flaw was found in the Linux kernel's CAPI over Bluetooth connection code. An attacker with a local account can escalate privileges when CAPI (ISDN) hardware connection fails.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
To mitigate these vulnerabilities on the operating system level, disable the Bluetooth functionality via blocklisting kernel modules in the Linux kernel. The kernel modules can be prevented from being loaded by using system-wide modprobe rules. Instructions on how to disable Bluetooth modules are available on the Customer Portal at https://access.redhat.com/solutions/2682931.
Alternatively, Bluetooth can be disabled within the hardware or at BIOS level which will also provide an effective mitigation as the kernel will not be able to detect that Bluetooth hardware is present on the system.
CVSS / CWE
CVSS 3.1 · 7.5CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
CWE-416 · Use After Free