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Fencer Vulns
medium 6.3

CVE-2016-7777 json

Xen 4.7.x and earlier does not properly honor CR0.TS and CR0.EM, which allows local x86 HVM guest OS users to read or modify FPU, MMX, or X…

published 2016-10-07 10 y ago modified 2026-06-17 4 mo ago also EUVD-2016-8627

cvss
6.3
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 23%
public exploits
0
none known

Summary

Xen 4.7.x and earlier does not properly honor CR0.TS and CR0.EM, which allows local x86 HVM guest OS users to read or modify FPU, MMX, or XMM register state information belonging to arbitrary tasks on the guest by modifying an instruction while the hypervisor is preparing to emulate it.

Patch / fix

  • xen Debian 14, Debian 13, Debian 12 4.8.0~rc3-1

debian advisories DEBIAN-CVE-2016-7777

  • xen Ubuntu 14.04 LTS 4.4.2-0ubuntu0.14.04.7
  • xen Ubuntu 16.04 LTS 4.6.0-1ubuntu4.2

ubuntu advisories UBUNTU-CVE-2016-7777

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

  • xen SLES 11 SP3-LTSS, SLE Point of Sale 11 SP3, OpenStack Cloud 5 +2 more 4.2.5_21-30.1
  • xen SLES for SAP 11 SP4, SLES 11 SP4, SLE Software Development Kit 11 SP4 4.4.4_10-43.5
  • xen SLES for SAP 12 SP1, SLES 12 SP1, SLED 12 SP1 +1 more 4.5.5_02-22.3.1
  • xen SLES for SAP 12 SP2, SLES 12 SP2, SLED 12 SP2 +1 more 4.7.1_02-25.1
  • xen SLES for SAP 12, SLES 12-LTSS 4.4.4_05-22.25.1
  • xen SLES 11 SP2-LTSS 4.1.6_08-32.1

suse advisories SUSE-SU-2016:3273-1SUSE-SU-2016:3174-1SUSE-SU-2016:3156-1SUSE-SU-2016:3083-1SUSE-SU-2016:3067-1SUSE-SU-2016:3044-1

  • xen openSUSE Tumbleweed 4.15.1_01-1.2

opensuse advisories openSUSE-SU-2024:11520-1

  • xen Alpine 3.24, Alpine 3.23, Alpine 3.22 +17 more 4.7.0-r5
  • xen Alpine 3.4 4.6.3-r3

alpine advisories ALPINE-CVE-2016-7777

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

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-2016-7777 updated cvss 6.1

xen: CR0.TS and CR0.EM not always honored for x86 HVM guests (XSA-190)

  • Red Hat Enterprise Linux 5 xen
    affected: no fix planned “Will not fix”

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

0.30% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 6.3 CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
NVD 2.0 3.3 AV:L/AC:M/Au:N/C:P/I:P/A:N

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization

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.