CVE-2020-25661: 
Linux Kernel vulnerability analysis and mitigation

CVE-2020-25661 is a Red Hat specific regression issue discovered in November 2020 that affects the Linux kernel's Bluetooth implementation. This vulnerability specifically impacts Red Hat Enterprise Linux 8.3 GA kernel version kernel-4.18.0-240.el8 and its derivatives. The issue emerged as a regression of the original CVE-2020-12351 vulnerability, which could not be included in the GA release due to timing constraints (BleedingTooth).

The vulnerability occurs in the way the Linux kernel's Bluetooth implementation handles L2CAP (Logical Link Control and Adaptation Protocol) packets with A2MP (Alternate MAC-PHY Manager Protocol) CID (Channel Identifier). The severity is rated as Important with a CVSS v3.1 base score of 8.8 HIGH (AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) (NVD).

A remote attacker within Bluetooth range can exploit this vulnerability to crash the system, causing a denial of service or potentially executing arbitrary code on the system by sending specially crafted L2CAP packets. The highest threat from this vulnerability is to system confidentiality, integrity, and availability (BleedingTooth).

The vulnerability requires the attacker to be in adjacent (Bluetooth) range of the target system and have knowledge of the system's MAC address. The attack can be executed by sending specially crafted L2CAP packets to the target system (BleedingTooth).

Red Hat recommends disabling Bluetooth functionality via blocklisting kernel modules in the Linux kernel using system-wide modprobe rules. Alternatively, Bluetooth can be disabled within the hardware or at BIOS level. Red Hat has released kernel updates to address this vulnerability through security advisories RHSA-2020:4685 and RHSA-2020:4686 (BleedingTooth).