CVE-2020-24490
Description
A heap buffer overflow flaw was found in the way the Linux kernel’s Bluetooth implementation processed extended advertising report events. This flaw allows a remote attacker in an adjacent range to crash the system, causing a denial of service or to potentially execute arbitrary code on the system by sending a specially crafted Bluetooth packet. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.
Security Bulletin
Statement
This issue is rated as having Moderate impact because the system needs to be actively scanning while the attacker is sending the advertisements in order to be exploited.
This issue only affects the Linux kernel version as shipped with the Red Hat Enterprise Linux 8.3 GA release, kernel-4.18.0-240.el8 (and any kernel derived from this release such as kernel rt-4.18.0-240.rt7.54.el8). Red Hat was unable to include the fixes in the GA release, as the Red Hat Enterprise Linux 8.3 GA release was in its final stages of release preparation when CVE-2020-24490 was made public. All of the subsequent Red Hat Enterprise Linux 8 kernel versions, including the version included in the so-called 0day (released on the same day or very close to that day) erratum, contain the fix, thus immune to this issue.
Mitigation
The only way to mitigate these vulnerabilities on the operating system level is to disable the Bluetooth functionality via blacklisting kernel modules in the Linux kernel. The kernel modules can be prevented from being loaded by using system-wide modprobe rules. How to disable Bluetooth modules instructions 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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.1 | 6.5 | N/A |
| Attack Vector | Adjacent Network | Adjacent Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | Required | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | None | N/A |
| Integrity Impact | High | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
Integrity,Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Modify Memory
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. Besides important user data, heap-based overflows can be used to overwrite function pointers that may be living in memory, pointing it to the attacker's code. Even in applications that do not explicitly use function pointers, the run-time will usually leave many in memory. For example, object methods in C++ are generally implemented using function pointers. Even in C programs, there is often a global offset table used by the underlying runtime.
Integrity,Confidentiality,Availability,Access Control,Other
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Other
When the consequence is arbitrary code execution, this can often be used to subvert any other security service.
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