CVE-2022-0001

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ModerateModerate ImpactWhat does this mean?
DescriptionStatementMitigationAdditional informationCVSS Score DetailsAcknowledgementsFAQ

Description

A flaw was found in hw. The Branch History Injection (BHI) describes a specific form of intra-mode BTI. This flaw allows an unprivileged attacker to manipulate the branch history before transitioning to supervisor or VMX root mode. This issue is an effort to cause an indirect branch predictor to select a specific predictor entry for an indirect branch, and a disclosure gadget at the predicted target will transiently execute. This execution is possible since the relevant branch history may contain branches taken in previous security contexts, and in particular, in other predictor modes.

Statement

The current known mechanisms to exploit this issue rely on unprivileged eBPF functionality. Unprivileged eBPF is disabled by default on Red Hat Enterprise Linux.

Mitigation

Disabling unprivileged eBPF effectively mitigates the known attack vectors for exploiting intra-mode branch injections attacks.

The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl.

For the Red Hat Enterprise Linux 7, the eBPF for unprivileged users is always disabled.

For the Red Hat Enterprise Linux 8 to confirm the current state, inspect the sysctl with the command:

# cat /proc/sys/kernel/unprivileged_bpf_disabled

The setting of 1 would mean that unprivileged users can not use eBPF, mitigating the flaw.

Continue to enable SMEP and Enhanced IBRS. This is the default setting on eligible CPUs.

Additional information

  • Bugzilla 2061712: hw: cpu: intel: Branch History Injection (BHI)
  • FAQ: Frequently asked questions about CVE-2022-0001

Common Vulnerability Scoring System (CVSS) Score Details

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 HatNVD

CVSS v3 Base Score

4.7

6.5

Attack Vector

Local

Local

Attack Complexity

High

Low

Privileges Required

Low

Low

User Interaction

None

None

Scope

Unchanged

Changed

Confidentiality Impact

High

High

Integrity Impact

None

None

Availability Impact

None

None

CVSS v3 Vector

Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Acknowledgements

Red Hat would like to thank Intel for reporting this issue.

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?

  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • "Affected" means that our Analysis Team has determined that this product is affected by this vulnerability and might release a fix to address this in the near future.

What can I do if my product is listed as "Will not fix"?

A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our Red Hat Vulnerability Scanner Certification program.

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