Description

x86: Speculative vulnerabilities with bare (non-shim) 32-bit PV guests 32-bit x86 PV guest kernels run in ring 1. At the time when Xen was developed, this area of the i386 architecture was rarely used, which is why Xen was able to use it to implement paravirtualisation, Xen's novel approach to virtualization. In AMD64, Xen had to use a different implementation approach, so Xen does not use ring 1 to support 64-bit guests. With the focus now being on 64-bit systems, and the availability of explicit hardware support for virtualization, fixing speculation issues in ring 1 is not a priority for processor companies. Indirect Branch Restricted Speculation (IBRS) is an architectural x86 extension put together to combat speculative execution sidechannel attacks, including Spectre v2. It was retrofitted in microcode to existing CPUs. For more details on Spectre v2, see: http://xenbits.xen.org/xsa/advisory-254.html However, IBRS does not architecturally protect ring 0 from predictions learnt in ring 1. For more details, see: https://software.intel.com/security-software-guidance/deep-dives/deep-dive-indirect-branch-restricted-speculation Similar situations may exist with other mitigations for other kinds of speculative execution attacks. The situation is quite likely to be similar for speculative execution attacks which have yet to be discovered, disclosed, or mitigated.

Severity

 

CVSS Version 3.x CVSS Version 2.0

CVSS 3.x Severity and Metrics:

NIST: NVD

Base Score:  5.5 MEDIUM

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

NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: NVD Analysts have published a CVSS score for this CVE based on publicly available information at the time of analysis. The CNA has not provided a score within the CVE List.

CVSS 2.0 Severity and Metrics:

NIST: NVD

Base Score:  2.1 LOW

Vector:  (AV:L/AC:L/Au:N/C:P/I:N/A:N)

NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: NVD Analysts have published a CVSS score for this CVE based on publicly available information at the time of analysis. The CNA has not provided a score within the CVE List.

References to Advisories, Solutions, and Tools

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Hyperlink	Resource
https://xenbits.xenproject.org/xsa/advisory-370.txt	Vendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-119	Improper Restriction of Operations within the Bounds of a Memory Buffer	NIST

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Change History

1 change records found show changes

Initial Analysis by NIST 6/24/2021 1:46:13 PM

Action	Type	Old Value	New Value
Added	CPE Configuration		OR *cpe:2.3:o:xen:xen:*:*:*:*:*:*:*:* versions up to (excluding) 4.12.0
Added	CVSS V2		NIST (AV:L/AC:L/Au:N/C:P/I:N/A:N)
Added	CVSS V3.1		NIST AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Added	CWE		NIST CWE-119
Changed	Reference Type	https://xenbits.xenproject.org/xsa/advisory-370.txt No Types Assigned	https://xenbits.xenproject.org/xsa/advisory-370.txt Vendor Advisory