CVE-2021-34981 - Vulnerability Details - OpenCVE

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.

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required High

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

Attack Vector Local

Attack Complexity High

Privileges Required High

Scope Changed

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v2

This CVE is not in the KEV list.

Key SSVC decision points have not yet been added.

Vendors	Products
Linux	Kernel Linux Kernel

Configuration 1 [-]

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

No data.

References

Link	Providers
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3cfdf8fcaafa62a4123f92eb0f4a72650da3a479
https://nvd.nist.gov/vuln/detail/CVE-2021-34981
https://www.cve.org/CVERecord?id=CVE-2021-34981
https://www.zerodayinitiative.com/advisories/ZDI-21-1223/

History

Thu, 14 Aug 2025 06:30:00 +0000

Type	Values Removed	Values Added
First Time appeared		Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux linux Kernel
Metrics	cvssV3_1 `{'score': 7.5, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H'}`	cvssV3_1 `{'score': 6.7, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H'}`

MITRE

Status: PUBLISHED

Assigner: zdi

Published: 2024-05-07T22:54:49.205Z

Updated: 2024-08-04T00:26:55.716Z

Reserved: 2021-06-17T19:27:05.661Z

Link: CVE-2021-34981

Vulnrichment

Updated: 2024-08-04T00:26:55.716Z

NVD

Status : Analyzed

Published: 2024-05-07T23:15:13.173

Modified: 2025-08-14T01:42:25.163

Link: CVE-2021-34981

Redhat

Severity : Moderate

Publid Date: 2021-10-25T00:00:00Z

Links: CVE-2021-34981 - Bugzilla

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{"bugzilla": {"description": "kernel: Bluetooth CMTP Module Double Free Privilege Escalation Vulnerability", "id": "2017077", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2017077"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-416", "details": ["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.\nThe 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.", "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."], "mitigation": {"lang": "en:us", "value": "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.\nAlternatively, 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."}, "name": "CVE-2021-34981", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2021-10-25T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-34981\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-34981\nhttps://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3cfdf8fcaafa62a4123f92eb0f4a72650da3a479"], "threat_severity": "Moderate"}