Vulnerability identifier: #VU31976

Vulnerability risk: Low

CVSSv3.1: 5.4 [CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2019-19577

CWE-ID: CWE-20

Exploitation vector: Local network

Exploit availability: No

Vulnerable software:
Xen
Server applications / Virtualization software

Vendor: Xen Project

Description

The vulnerability allows a remote user to perform a denial of service (DoS) attack.

An issue was discovered in Xen through 4.12.x allowing x86 AMD HVM guest OS users to cause a denial of service or possibly gain privileges by triggering data-structure access during pagetable-height updates. When running on AMD systems with an IOMMU, Xen attempted to dynamically adapt the number of levels of pagetables (the pagetable height) in the IOMMU according to the guest's address space size. The code to select and update the height had several bugs. Notably, the update was done without taking a lock which is necessary for safe operation. A malicious guest administrator can cause Xen to access data structures while they are being modified, causing Xen to crash.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Xen: 4.8.0 - 4.12.0

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External links
http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00011.html
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/34HBFTYNMQMWIO2GGK7DB6KV4M6R5YPV/
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/D5R73AYE53QA32KTMHUVKCX6E52CIS43/
http://seclists.org/bugtraq/2020/Jan/21
http://security.gentoo.org/glsa/202003-56
http://www.debian.org/security/2020/dsa-4602
http://xenbits.xen.org/xsa/advisory-311.html

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated privileged user via the local network (LAN).

Is there known malware, which exploits this vulnerability?

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