UBUNTU-CVE-2026-79603

    Dashboard / Vulnerabilities / UBUNTU-CVE-2026-79603

    UBUNTU-CVE-2026-79603

    Published: 8 Sept 2026Last Modified: 10 Sept 2026
    Upstream:
    CVE-2026-79603

    Summary:

    Details: x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page. Deployments using `xsm=silo scrub-domheap` with the aim of not allowing the exchange of information amongst guests are not effective in the presence of PV guests. All Xen versions from 4.13 onwards are vulnerable. Xen versions 4.12 and earlier are not vulnerable as they lack the `scrub-domheap` command line option. Only x86 PV guests can exploit the vulnerability.

    References: https://ubuntu.com/security/CVE-2026-79603, https://www.cve.org/CVERecord?id=CVE-2026-79603

    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-2026-79603 | CVE-DB