HOMEVULNERABILITIESCVE-2016-4020
MEDIUM

CVE-2016-4020

NVD-CWE-noinfoPublished: May 25, 2016· Updated: Jun 17, 2026

6.5
CVSS v3.1

Official 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).

NVD Source

Technical Analysis

CVE-2016-4020 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in complete confidentiality breach (data exposure), with a CVSS base score of 6.5.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorLocal
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeChanged
Impact
ConfidentialityHigh
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Affected Vendors & Products

Canonical1 product(s)
ubuntu linux
Debian1 product(s)
debian linux
qemu1 product(s)
qemu
Red Hat9 product(s)
openstackenterprise linux desktopenterprise linux eusenterprise linux serverenterprise linux server ausenterprise linux server tusenterprise linux workstationvirtualizationenterprise linux
Source: NVD CPE · 26 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
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Official Patches & Advisories

All References (22)

Quick Facts

CVE IDCVE-2016-4020
CVSS Score6.5 / 10
SeverityMEDIUM
CISA KEVNo
Affected4 vendor(s)
PublishedMay 25, 2016

Related CVEs (NVD-CWE-noinfo)

Recommended Actions

  • Apply vendor patches immediately
  • Monitor CVE-2016-4020 in threat intel feeds
  • Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.