CVE-2021-34981 Linux Kernel Bluetooth CMTP Module Double Free Privilege Escalation Vulnerability

What is CVE-2021-34981?

CVE-2021-34981 is a high-severity use after free vulnerability in Linux kernel, published on 7 May 2024. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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.

Weakness: CWE-415

Which versions are affected by CVE-2021-34981?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2021-34981?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2021-34981 being exploited?

There is no known exploitation of CVE-2021-34981 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as CVE-2021-3534, DEBIAN-CVE-2021-34981, GHSA-98qh-xfx7-vfqv, UBUNTU-CVE-2021-34981.