Skip to main content
MEDIUM

CVE-2021-3631

CVSS v3

6.3

MEDIUM

EPSS Score

0.5 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

Get an alert for each new CVE published for libvirt.

Set up CVE WatchFree account · no credit card

Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • hivexAlmaLinux:8all versions · fixed in 1.3.18-21.module_el8.5.0+2608+72063365and 4 other packages
  • libguestfsAlmaLinux:8all versions · fixed in 1:1.40.2-28.module_el8.5.0+2608+72063365.almaand 23 other packages
  • libguestfs-winsupportAlmaLinux:8all versions · fixed in 8.2-1.module_el8.5.0+2608+72063365
  • libiscsiAlmaLinux:8all versions · fixed in 1.18.0-8.module_el8.5.0+2608+72063365and 2 other packages
  • libnbdAlmaLinux:8all versions · fixed in 1.2.2-1.module_el8.5.0+2608+72063365and 3 other packages
  • libvirtAlmaLinux:8all versions · fixed in 6.0.0-37.module_el8.5.0+2608+72063365and 28 other packages
  • libvirt-dbusAlmaLinux:8all versions · fixed in 1.3.0-2.module_el8.5.0+2608+72063365
  • nbdkitAlmaLinux:8all versions · fixed in 1.16.2-4.module_el8.5.0+2608+72063365and 13 other packages

6 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-3631 Red Hat Product Security2,713 products fixed · 132 known affected

    libvirt: Insecure sVirt label generation

    libvirt as a component of Red Hat Enterprise Linux 6 · libvirt-client as a component of Red Hat Enterprise Linux 6 · libvirt-devel as a component of Red Hat Enterprise Linux 6

  • RHSA-2021:4191 Red Hat Product Security838 products fixed

    Red Hat Security Advisory: virt:rhel and virt-devel:rhel security, bug fix, and enhancement update

  • RHSA-2021:3704 Red Hat Product Security918 products fixed

    Red Hat Security Advisory: virt:8.2 and virt-devel:8.2 security update

  • RHSA-2021:3703 Red Hat Product Security957 products fixed

    Red Hat Security Advisory: virt:av and virt-devel:av security and bug fix update

Full record on NVD

Description

A flaw was found in libvirt while it generates SELinux MCS category pairs for VMs' dynamic labels. This flaw allows one exploited guest to access files labeled for another guest, resulting in the breaking out of sVirt confinement. The highest threat from this vulnerability is to confidentiality and integrity.

Technical details

Published
2022-03-02

Frequently asked questions

What is CVE-2021-3631?

A flaw was found in libvirt while it generates SELinux MCS category pairs for VMs' dynamic labels. This flaw allows one exploited guest to access files labeled for another guest, resulting in the breaking out of sVirt confinement. The highest threat from this vulnerability is to confidentiality and integrity.

Is CVE-2021-3631 actively exploited?

Active exploitation of CVE-2021-3631 has not been confirmed. Its EPSS score was 0.5% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-3631?

CVE-2021-3631 has a CVSS v3 base score of 6.3 (MEDIUM severity).

Running libvirt? Hear about its next vulnerability

CVE Watch matches each new CVE to the vendors and products you list (vendor and product, not the version) and puts it in your alerts with its KEV and EPSS status.

Get alerts for this productCISA KEV additions, October 2026Search CVEs

Already have an account? Open CVE WatchNo credit card required · No monthly cap on website lookups · 250 API requests/month

Go further

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database