UBUNTU-CVE-2021-26933

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    UBUNTU-CVE-2021-26933

    Published: 17 Feb 2021Last Modified: 17 Oct 2026
    Upstream:
    CVE-2021-26933

    Summary:

    Details: 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.

    References: https://ubuntu.com/security/CVE-2021-26933, https://www.openwall.com/lists/oss-security/2021/02/16/5, https://xenbits.xen.org/xsa/advisory-364.html, https://www.cve.org/CVERecord?id=CVE-2021-26933

    Affected packages

    Package

    Name: xen

    Purl: pkg:deb/ubuntu/xen?arch=source&distro=xenial

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 0
    Fixed -None

    Affected versions

    4.5.1-0ubuntu1
    4.5.1-0ubuntu2

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    UBUNTU-CVE-2021-26933 | CVE-DB