Vulnerability Name:

CVE-2021-26933 (CCN-196829)

Assigned:2021-02-16
Published:2021-02-16
Updated:2022-05-27
Summary:An issue was discovered in Xen 4.9 through 4.14.x. On Arm, a guest is allowed to control whether memory accesses are bypassing the cache. This means that Xen needs to ensure that all writes (such as the ones during scrubbing) have reached the memory before handing over the page to a guest. Unfortunately, the operation to clean the cache is happening before checking if the page was scrubbed. Therefore there is no guarantee when all the writes will reach the memory.
CVSS v3 Severity:5.5 Medium (CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N)
4.8 Medium (Temporal CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/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): Unchanged
Impact Metrics:Confidentiality (C): High
Integrity (I): None
Availibility (A): None
6.2 Medium (CCN CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N)
5.4 Medium (CCN Temporal CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/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): None
User Interaction (UI): None
Scope:Scope (S): Unchanged
Impact Metrics:Confidentiality (C): High
Integrity (I): None
Availibility (A): None
CVSS v2 Severity:2.1 Low (CVSS v2 Vector: AV:L/AC:L/Au:N/C:P/I:N/A:N)
Exploitability Metrics:Access Vector (AV): Local
Access Complexity (AC): Low
Authentication (Au): None
Impact Metrics:Confidentiality (C): Partial
Integrity (I): None
Availibility (A): None
4.9 Medium (CCN CVSS v2 Vector: AV:L/AC:L/Au:N/C:C/I:N/A:N)
Exploitability Metrics:Access Vector (AV): Local
Access Complexity (AC): Low
Athentication (Au): None
Impact Metrics:Confidentiality (C): Complete
Integrity (I): None
Availibility (A): None
Vulnerability Type:CWE-noinfo
Vulnerability Consequences:Obtain Information
References:Source: MITRE
Type: CNA
CVE-2021-26933

Source: CCN
Type: Xen Security Advisory XSA-364
arm: The cache may not be cleaned for newly allocated scrubbed pages

Source: MISC
Type: Patch, Vendor Advisory
http://xenbits.xen.org/xsa/advisory-364.html

Source: XF
Type: UNKNOWN
xen-cve202126933-info-disc(196829)

Source: FEDORA
Type: Mailing List, Third Party Advisory
FEDORA-2021-4c819bf1ad

Source: FEDORA
Type: Mailing List, Third Party Advisory
FEDORA-2021-47f53a940a

Source: DEBIAN
Type: Third Party Advisory
DSA-4888

Vulnerable Configuration:Configuration 1:
  • cpe:/o:xen:xen:*:*:*:*:*:*:arm:* (Version >= 4.9.0 and <= 4.14.1)

    • Configuration 2:
  • cpe:/o:fedoraproject:fedora:32:*:*:*:*:*:*:*
  • OR cpe:/o:fedoraproject:fedora:33:*:*:*:*:*:*:*

    • Configuration 3:
  • cpe:/o:debian:debian_linux:10.0:*:*:*:*:*:*:*

    • Configuration CCN 1:
  • cpe:/a:xensource:xen:4.9:*:*:*:*:*:*:*
  • OR cpe:/a:xensource:xen:4.11:*:*:*:*:*:*:*
  • OR cpe:/a:xensource:xen:4.10:*:*:*:*:*:*:*

    • * Denotes that component is vulnerable
    BACK
    xen xen *
    fedoraproject fedora 32
    fedoraproject fedora 33
    debian debian linux 10.0
    xensource xen 4.9
    xensource xen 4.11
    xensource xen 4.10