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Fencer Vulns
medium 6.5

CVE-2016-4020 json

The patch_instruction function in hw/i386/kvmvapic.c in QEMU does not initialize the imm32 variable, which allows local guest OS administra…

published 2016-05-25 10 y ago modified 2026-06-17 4 mo ago also EUVD-2016-5026

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 31%
public exploits
0
none known

Summary

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).

Patch / fix

  • qemu Debian 14, Debian 13, Debian 12 1:2.6+dfsg-2

debian advisories DEBIAN-CVE-2016-4020

  • qemu Ubuntu 14.04 LTS 2.0.0+dfsg-2ubuntu1.24
  • qemu Ubuntu 16.04 LTS 1:2.5+dfsg-5ubuntu10.1

ubuntu advisories UBUNTU-CVE-2016-4020

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • qemu-kvm RHEL 7 10:1.5.3-141.el7
  • qemu-img RHEL 7 10:1.5.3-141.el7
  • qemu-kvm-tools RHEL 7 10:1.5.3-141.el7
  • qemu-kvm-common RHEL 7 10:1.5.3-141.el7
  • qemu-kvm-rhev openstack 11, openstack 10, openstack 9 +3 more 10:2.9.0-10.el7
  • qemu-img-rhev openstack 11, openstack 10, openstack 9 +3 more 10:2.9.0-10.el7
  • qemu-kvm-tools-rhev openstack 11, openstack 10, openstack 9 +3 more 10:2.9.0-10.el7
  • qemu-kvm-common-rhev openstack 11, openstack 10, openstack 9 +3 more 10:2.9.0-10.el7

red hat advisories RHSA-2017:1856RHSA-2017:2408RHSA-2017:2392

  • xen SLES for SAP 11 SP4, SLES 11 SP4, SLE Software Development Kit 11 SP4 4.4.4_07-37.1
  • xen SLES for SAP 12 SP1, SLES 12 SP1, SLED 12 SP1 +1 more 4.5.3_08-17.1
  • kvm SLES for SAP 11 SP4, SLES 11 SP4 1.4.2-44.1
  • qemu SLES for SAP 12 SP1, SLES 12 SP1, SLED 12 SP1 2.3.1-14.1
  • kvm SLES 11 SP3-TERADATA, SLES 11 SP3-LTSS 1.4.2-46.1
  • qemu SLES for SAP 12, SLES 12, SLED 12 2.0.2-48.19.1
  • xen SLES for SAP 12, SLES 12-LTSS 4.4.4_04-22.22.2

suse advisories SUSE-SU-2016:2533-1SUSE-SU-2016:2100-1SUSE-SU-2016:2093-1SUSE-SU-2016:1785-1SUSE-SU-2016:1703-1SUSE-SU-2016:1698-1

  • qemu openSUSE Tumbleweed 2.6.1-1.5
  • qemu-linux-user openSUSE Tumbleweed 2.6.1-1.5

opensuse advisories openSUSE-SU-2024:10233-1openSUSE-SU-2024:10285-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2016-4020 updated cvss 3.4

Qemu: i386: leakage of stack memory to guest in kvmvapic.c

  • Red Hat Enterprise Linux OpenStack Platform 5 (Icehouse) qemu-kvm-rhev
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux Client (v. 7) qemu-img 1.5.3-141.el7, qemu-kvm 1.5.3-141.el7, qemu-kvm-tools 1.5.3-141.el7, qemu-kvm-common 1.5.3-141.el7 Red Hat Enterprise Linux ComputeNode Optional (v. 7) qemu-img 1.5.3-141.el7, qemu-kvm 1.5.3-141.el7, qemu-kvm-tools 1.5.3-141.el7, qemu-kvm-common 1.5.3-141.el7
    fixed: vendor fix RHSA-2017:1856
  • Red Hat Enterprise Linux OpenStack Platform 6.0 (Juno) for RHEL 7 qemu-img-rhev 2.9.0-10.el7, qemu-kvm-rhev 2.9.0-10.el7, qemu-kvm-tools-rhev 2.9.0-10.el7, qemu-kvm-common-rhev 2.9.0-10.el7 Red Hat Enterprise Linux OpenStack Platform 7.0 (Kilo) for RHEL 7 qemu-img-rhev 2.9.0-10.el7, qemu-kvm-rhev 2.9.0-10.el7, qemu-kvm-tools-rhev 2.9.0-10.el7, qemu-kvm-common-rhev 2.9.0-10.el7
    fixed: vendor fix RHSA-2017:2408
  • Red Hat Enterprise Linux Server (v. 7) qemu-img 1.5.3-141.el7, qemu-kvm 1.5.3-141.el7, qemu-kvm-tools 1.5.3-141.el7, qemu-kvm-common 1.5.3-141.el7 Red Hat Enterprise Linux Workstation (v. 7) qemu-img 1.5.3-141.el7, qemu-kvm 1.5.3-141.el7, qemu-kvm-tools 1.5.3-141.el7, qemu-kvm-common 1.5.3-141.el7
    fixed: vendor fix RHSA-2017:1856
  • Red Hat OpenStack Platform 8.0 (Liberty) qemu-img-rhev 2.9.0-10.el7, qemu-kvm-rhev 2.9.0-10.el7, qemu-kvm-tools-rhev 2.9.0-10.el7, qemu-kvm-common-rhev 2.9.0-10.el7 Red Hat OpenStack Platform 9.0 qemu-img-rhev 2.9.0-10.el7, qemu-kvm-rhev 2.9.0-10.el7, qemu-kvm-tools-rhev 2.9.0-10.el7, qemu-kvm-common-rhev 2.9.0-10.el7 Red Hat OpenStack Platform 10.0 qemu-img-rhev 2.9.0-10.el7, qemu-kvm-rhev 2.9.0-10.el7, qemu-kvm-tools-rhev 2.9.0-10.el7, qemu-kvm-common-rhev 2.9.0-10.el7 Red Hat OpenStack Platform 11.0 qemu-img-rhev 2.9.0-10.el7, qemu-kvm-rhev 2.9.0-10.el7, qemu-kvm-tools-rhev 2.9.0-10.el7, qemu-kvm-common-rhev 2.9.0-10.el7
    fixed: vendor fix RHSA-2017:2408
  • Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts qemu-img-rhev 2.9.0-14.el7, qemu-kvm-rhev 2.9.0-14.el7, qemu-kvm-tools-rhev 2.9.0-14.el7, qemu-kvm-common-rhev 2.9.0-14.el7
    fixed: vendor fix RHSA-2017:2392
  • Red Hat Enterprise Linux 5 kvm, xen Red Hat Enterprise Linux 6 qemu-img, qemu-kvm, qemu-kvm-tools, qemu-guest-agent, qemu-guest-agent-win32 Red Hat OpenStack Platform 12 (Pike) qemu-img-rhev, qemu-kvm-rhev, qemu-kvm-tools-rhev, qemu-kvm-common-rhev
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.37% chance of exploitation in the next 30 days, higher than 31% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:P/I:N/A:N

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.