Privilege escalation in Xen

1) Use-after-free

EUVDB-ID: #VU57097

Risk: Medium

CVSSv3.1: 5.8 [CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-28702

CWE-ID: CWE-416 - Use After Free

Exploit availability: No

Description

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.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Xen: 4.4.0 - 4.15.1

External links

http://xenbits.xen.org/xsa/advisory-386.html

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated privileged user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.