CVE-2021-3631

Exp

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.

Published: 2022-03-02 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-3631 is rated Exploit Available (54/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.49%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-3631

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-3631

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.05% 0.49% +0.44%
2 2025-12-02 0.05% 0.05% +0.01%
3 2025-11-21 — 0.05% —

Full EPSS history (11 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3631

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.3 3.1 MEDIUM
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 1.0 5.2 [email protected]
3.3 2.0 LOW
AV:L/AC:M/Au:N/C:P/I:P/A:N Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 3.4 4.9 [email protected]

Weakness enumeration for CVE-2021-3631

OS Trackers for CVE-2021-3631

vendor priority summary link
alpine — CVE-2021-3631: 1 source package rows (libvirt); 14 state rows across 8 repos (3.12-main, 3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 7, open 7. https://security.alpinelinux.org/vuln/CVE-2021-3631
debian not yet assigned CVE-2021-3631 not yet assigned priority: Debian including 1 source packages (libvirt), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-3631
gentoo low CVE-2021-3631: 1 GLSA(s) (202210-06), 2 atom(s) (app-emulation/libvirt, dev-python/libvirt-python); latest impact low. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-3631
redhat low — https://access.redhat.com/security/cve/CVE-2021-3631
suse medium CVE-2021-3631 severity moderate: SUSE including 629 source package names (0.45.0.7.7.1:libvirt-libs-7.1.0-6.5.1, 0.45.0.8.14.1:libvirt-client-7.1.0-6.5.1, …), 1363 product×package rows across 69 product lines (Container suse/sles/15.3/libguestfs-tools, Container suse/sles/15.3/virt-handler, … (69 product lines)): Known Not Affected 645, Fixed 487, Known Affected 231. https://www.suse.com/security/cve/CVE-2021-3631/
ubuntu negligible CVE-2021-3631 negligible priority: Ubuntu including 1 source packages (libvirt), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): released 11, ignored 2, needs-triage 2, not-affected 1. https://ubuntu.com/security/CVE-2021-3631

Affected software / configurations for CVE-2021-3631

Vendor Product Version Raw CPE
redhat libvirt < 7.5.0 cpe:2.3:a:redhat:libvirt:*:*:*:*:*:*:*:*
redhat openshift_container_platform 4.8 cpe:2.3:a:redhat:openshift_container_platform:4.8:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:advanced_virtualization:*:*:*
netapp ontap_select_deploy_administration_utility — cpe:2.3:a:netapp:ontap_select_deploy_administration_utility:-:*:*:*:*:*:*:*

References for CVE-2021-3631

cvelogic Threat Intelligence