CVE-2016-4020
MEDIUMCVSS 6.5/10EPSS 0.38%
Last modified
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
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
- https://www.securityfocus.com/bid/86067Third Party Advisory, VDB Entry
- https://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
- https://www.securityfocus.com/bid/86067Third Party Advisory, VDB Entry
- https://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
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is CVE-2016-4020?
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).
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.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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Are you affected by CVE-2016-4020?
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