CVE-2021-28695 Privilege escalation in xen

Medium 6.8 Published 27 Aug 2021 Updated 3 Aug 2024

A flaw in Xen's IOMMU handling on AMD systems allows guests to retain unauthorized memory access, enabling privilege escalation and data exposure.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2021-28695?

CVE-2021-28695 is a medium-severity vulnerability in Debian Debian Linux, published on 27 Aug 2021. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

IOMMU page mapping issues on x86 T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] Both AMD and Intel allow ACPI tables to specify regions of memory which should be left untranslated, which typically means these addresses should pass the translation phase unaltered. While these are typically device specific ACPI properties, they can also be specified to apply to a range of devices, or even all devices. On all systems with such regions Xen failed to prevent guests from undoing/replacing such mappings (CVE-2021-28694). On AMD systems, where a discontinuous range is specified by firmware, the supposedly-excluded middle range will also be identity-mapped (CVE-2021-28695). Further, on AMD systems, upon de-assigment of a physical device from a guest, the identity mappings would be left in place, allowing a guest continued access to ranges of memory which it shouldn't have access to anymore (CVE-2021-28696).

Which versions are affected by CVE-2021-28695?

It affects 3 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Xen Xen.

How do I fix CVE-2021-28695?

Apply the vendor's patch.

Is CVE-2021-28695 being exploited?

There is no known exploitation of CVE-2021-28695 in the wild and no public exploit code.

All Debian Debian Linux vulnerabilities

Sources

Also known as ALPINE-CVE-2021-28695, DEBIAN-CVE-2021-28695, GHSA-c3qw-gwpv-g4fw, UBUNTU-CVE-2021-28695.