CVE-2021-28689

Published on: 06/11/2021 12:00:00 AM UTC

Last Modified on: 06/24/2021 05:46:00 PM UTC

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

Certain versions of Xen from Xen contain the following vulnerability:

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.

  • CVE-2021-28689 has been assigned by URL Logo [email protected] to track the vulnerability - currently rated as MEDIUM severity.
  • Affected Vendor/Software: URL Logo Xen - Xen version ?< 4.12

CVSS3 Score: 5.5 - MEDIUM

Attack
Vector
Attack
Complexity
Privileges
Required
User
Interaction
LOCAL LOW LOW NONE
Scope Confidentiality
Impact
Integrity
Impact
Availability
Impact
UNCHANGED HIGH NONE NONE

CVSS2 Score: 2.1 - LOW

Access
Vector
Access
Complexity
Authentication
LOCAL LOW NONE
Confidentiality
Impact
Integrity
Impact
Availability
Impact
PARTIAL NONE NONE

CVE References

Description Tags Link
xenbits.xenproject.org
text/plain
URL Logo MISC xenbits.xenproject.org/xsa/advisory-370.txt

Related QID Numbers

  • 750030 SUSE Enterprise Linux Security Update for xen (SUSE-SU-2021:1648-1)

Known Affected Configurations (CPE V2.3)

Type Vendor Product Version Update Edition Language
Operating
System
XenXenAllAllAllAll
  • cpe:2.3:o:xen:xen:*:*:*:*:*:*:*:*:

Social Mentions

Source Title Posted (UTC)
Twitter Icon @CVEreport CVE-2021-28689 : x86: Speculative vulnerabilities with bare non-shim 32-bit PV guests 32-bit x86 PV guest… twitter.com/i/web/status/1… 2021-06-11 14:58:48
Twitter Icon @LinInfoSec Xen - CVE-2021-28689: xenbits.xenproject.org/xsa/advisory-3… 2021-06-11 17:11:24
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