Vulnerability Name:

CVE-2021-28689 (CCN-201170)

Assigned:2021-05-04
Published:2021-05-04
Updated:2021-06-11
Summary: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.
CVSS v3 Severity:6.5 Medium (CCN CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N)
5.7 Medium (CCN Temporal CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N/E:U/RL:O/RC:C)
Exploitability Metrics:Attack Vector (AV): Local
Attack Complexity (AC): Low
Privileges Required (PR): Low
User Interaction (UI): None
Scope:Scope (S): Changed
Impact Metrics:Confidentiality (C): High
Integrity (I): None
Availibility (A): None
CVSS v2 Severity:4.6 Medium (CCN CVSS v2 Vector: AV:L/AC:L/Au:S/C:C/I:N/A:N)
Exploitability Metrics:Access Vector (AV): Local
Access Complexity (AC): Low
Athentication (Au): Single_Instance
Impact Metrics:Confidentiality (C): Complete
Integrity (I): None
Availibility (A): None
Vulnerability Consequences:Obtain Information
References:Source: MITRE
Type: CNA
CVE-2021-28689

Source: CCN
Type: Xen Security Advisory XSA-370
x86: Speculative vulnerabilities with bare (non-shim) 32-bit PV guests

Source: XF
Type: UNKNOWN
xen-cve202128689-info-disc(201170)

Source: MISC
Type: UNKNOWN
https://xenbits.xenproject.org/xsa/advisory-370.txt

Vulnerable Configuration:Configuration CCN 1:
  • cpe:/a:xensource:xen:*:*:*:*:*:*:*:*

  • * Denotes that component is vulnerable
    BACK
    xensource xen *