Use-after-free in Xen - CVE-2021-28702

Vulnerability identifier: #VU57097

CSH Severity: Medium

CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

CVE-ID: CVE-2021-28702

CWE-ID: CWE-416

Exploitation vector: Remote access

Exploit availability: No public exploit available

Affected software:
Xen
SUSE MicroOS
SUSE Linux Enterprise Software Development Kit
SUSE Linux Enterprise Server
SUSE Linux Enterprise Module for Server Applications
SUSE Linux Enterprise Module for Basesystem
Fedora
xen-tools
xen-debugsource
xen-tools-domU-debuginfo
xen-tools-domU
xen-tools-debuginfo
xen-libs-debuginfo
xen-libs-debuginfo-32bit
xen-libs
xen-libs-32bit
xen-doc-html
xen
xen-devel
xen-tools-xendomains-wait-disk

The vulnerability allows a remote user to perform a escalate privileges on the system.

The vulnerability exists due to a design error in PCI devices with RMRRs. If such device is connected through to a guest OS, then on guest OS shutdown of the device is not properly deassigned.  The IOMMU configuration for these devices which are not properly deassigned ends up pointing to a freed data structure, including the IO Pagetables.

Subsequent DMA or interrupts from the device will have unpredictable behaviour, ranging from IOMMU faults to memory corruption.

Administrators of guests which have been assigned RMRR-using PCI devices can cause denial of service and other problems, possibly including escalation of privilege.

Install updates from vendor's website.

• https://xenbits.xen.org/xsa/advisory-386.html