CVE-2018-9056
BranchScope is a new class of attack which leverages functioning of the Branch Prediction Unit (BPU) of a processor to infer/leak sensitive process information, which is involved in the branch decision making (if (x) { x ^ y; } else {x & y;}). In this, BranchScope side-channel could help to infer 'x', by observing prediction patterns of the Branch Prediction Unit (BPU).
Find out more about CVE-2018-9056 from the MITRE CVE dictionary dictionary and NIST NVD.
CVSS v3 metrics
NOTE: The following CVSS v3 metrics and score provided are preliminary and subject to review.
| CVSS3 Base Score | 5.6 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N |
| Attack Vector | Local |
| Attack Complexity | High |
| Privileges Required | Low |
| User Interaction | None |
| Scope | Changed |
| Confidentiality | High |
| Integrity Impact | None |
| Availability Impact | None |
Affected Packages State
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise MRG 2 | realtime-kernel | Not affected |
| Red Hat Enterprise Linux 7 | kernel-alt | Not affected |
| Red Hat Enterprise Linux 7 | kernel | Not affected |
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected |
| Red Hat Enterprise Linux 6 | kernel | Not affected |
| Red Hat Enterprise Linux 5 | kernel | Not affected |
Mitigation
This is a hardware processor issue, not a Linux kernel flaw. The flaw specifically targets software which uses sensitive information in branching expressions. A software mitigation could be for the target software to avoid the use of sensitive data bits in (if..else) branching decisions or to avoid (if..else) branching altogether.