CVE-2020-26556
Description
A flaw was found in the Linux kernel’s authentication protocol in the Bluetooth® Mesh Profile Specification. A vulnerability occurs if the AuthValue is identified during the provisioning procedure, even if the AuthValue is selected randomly. This flaw allows an attacker to identify the AuthValue used before the provisioning procedure times out, possibly completing the provisioning operation and obtaining a NetKey. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.
Statement
Red Hat Product Security is aware of this issue and is currently assessing the impact on Red Hat supported products. Corresponding entry in the Red Hat CVE database (https://access.redhat.com/security/security-updates/#/cve) will be updated with latest information as the assessment progresses.
Mitigation
It is recommended for devices to use AuthValues containing the maximum entropy permitted (128-bits) and randomly select a new AuthValue using a secure random number generator with each new provisioning attempt. A large entropy helps ensure that a brute of the AuthValue, even a static AuthValue, cannot be completed in a reasonable time.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | 7.5 | N/A |
| Attack Vector | Adjacent Network | Adjacent Network | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
An attacker could guess the random numbers generated and could gain unauthorized access to a system if the random numbers are used for authentication and authorization.
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