CVE-2016-4020

What it is

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).

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of data exposure.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2016-05-25 15:59 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 00:46 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 6.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2016-05-25 15:59 UTC

Last modified

2026-06-17 00:46 UTC

Exploit probability

0.4% · EPSS, next 30 days

Record status

Modified

Affected

• 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 Linux 8.0
• Redhat Openstack 6.0
• Redhat Openstack 7.0

Attack profile CVSS 3.1 · 6.5

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2016-4020.md and follow it. Check whether this project is affected by CVE-2016-4020. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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