CVE-2016-4020

Name: CVE-2016-4020
Creator: NVD / NIST
Published: 2016-05-25T15:59:04.927+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 0.38%

Last modified Jun 17, 2026

CVE-2016-4020 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. The patch_instruction function in hw/i386/kvmvapic.c in QEMU does not initialize the imm32 variable, which allows local guest OS administrators to obtain sensitive information from host stack memory by accessing the Task Priority Register (TPR).. EPSS estimates a 0.38% chance of exploitation in the next 30 days.

Description

The patch_instruction function in hw/i386/kvmvapic.c in QEMU does not initialize the imm32 variable, which allows local guest OS administrators to obtain sensitive information from host stack memory by accessing the Task Priority Register (TPR).

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

EPSS Probability

0.38%

29.3th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Qemu	Qemu	<= 2.6.2
Canonical	Ubuntu Linux	12.04
Canonical	Ubuntu Linux	14.04
Canonical	Ubuntu Linux	15.10
Canonical	Ubuntu Linux	16.04
Debian	Debian Linux	8.0
Redhat	Openstack	6.0
Redhat	Openstack	7.0
Redhat	Openstack	8
Redhat	Openstack	9
Redhat	Openstack	10
Redhat	Openstack	11
Redhat	Enterprise Linux Desktop	7.0
Redhat	Enterprise Linux Eus	7.4
Redhat	Enterprise Linux Eus	7.5
Redhat	Enterprise Linux Eus	7.6
Redhat	Enterprise Linux Eus	7.7
Redhat	Enterprise Linux Server	7.0
Redhat	Enterprise Linux Server Aus	7.4
Redhat	Enterprise Linux Server Aus	7.6
Redhat	Enterprise Linux Server Aus	7.7
Redhat	Enterprise Linux Server Tus	7.6
Redhat	Enterprise Linux Server Tus	7.7
Redhat	Enterprise Linux Workstation	7.0
Redhat	Virtualization	4.0

References

http://git.qemu.org/?p=qemu.git%3Ba=commit%3Bh=691a02e2ce0c413236a78dee6f2651c937b09fb0
http://www.securityfocus.com/bid/86067Third Party Advisory, VDB Entry
http://www.ubuntu.com/usn/USN-2974-1Third Party Advisory
https://access.redhat.com/errata/RHSA-2017:1856Third Party Advisory
https://access.redhat.com/errata/RHSA-2017:2392Third Party Advisory
https://access.redhat.com/errata/RHSA-2017:2408Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1313686Issue Tracking, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2018/11/msg00038.htmlMailing List, Third Party Advisory
https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg01106.htmlPatch, Third Party Advisory
https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg01118.htmlPatch, Third Party Advisory
https://security.gentoo.org/glsa/201609-01Third Party Advisory
http://git.qemu.org/?p=qemu.git%3Ba=commit%3Bh=691a02e2ce0c413236a78dee6f2651c937b09fb0
http://www.securityfocus.com/bid/86067Third Party Advisory, VDB Entry
http://www.ubuntu.com/usn/USN-2974-1Third Party Advisory
https://access.redhat.com/errata/RHSA-2017:1856Third Party Advisory
https://access.redhat.com/errata/RHSA-2017:2392Third Party Advisory
https://access.redhat.com/errata/RHSA-2017:2408Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1313686Issue Tracking, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2018/11/msg00038.htmlMailing List, Third Party Advisory
https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg01106.htmlPatch, Third Party Advisory
https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg01118.htmlPatch, Third Party Advisory
https://security.gentoo.org/glsa/201609-01Third Party Advisory

Timeline

Published: May 25, 2016
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2016-4020?

How severe is CVE-2016-4020?

CVE-2016-4020 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.38% probability of exploitation in the next 30 days.

How do I fix CVE-2016-4020?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2016-4020?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST