CVE-2021-3631

MEDIUMNVD 6.36.3—
EchelonGraph scoreMEDIUM confidence

Score 6.3 from GitHub Security Advisory published 2022-03-04. NVD baseline CVSS 6.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
6.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.3Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
6.3
EG Score
6.3(medium)
EPSS
39.2%
KEV
Not listed

Published

March 2, 2022

Last Modified

November 21, 2024

References (14)

Vendor Advisories for CVE-2021-3631(3)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibvirt-daemon-driver-storage-zfs (6.0.0-0ubuntu8.16) @ focal2026-05-26ubuntu
redhatvirt:rhel-8050020211001230723.b4937e532021-11-09redhat
redhatvirt-devel:8.2-8020120210917153657.863bb0db2021-09-30redhat
redhatvirt-devel:av-8040020210922084349.522a0ee42021-09-30redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(2)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 12× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 102 total refreshes for this CVE.

  1. 2026-07-21 15:22 UTCEPSS rescore
  2. 2026-07-21 15:22 UTCEPSS rescore
  3. 2026-07-20 17:05 UTCEPSS rescore
  4. 2026-07-19 14:29 UTCEPSS rescore
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  8. 2026-07-17 21:59 UTCOSV refresh
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  1. 2026-07-06 02:21 UTCEPSS rescore
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  8. 2026-06-30 23:20 UTCEPSS rescore
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  10. 2026-06-29 19:32 UTCOSV refresh
  11. 2026-06-29 14:04 UTCEPSS rescore
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  23. 2026-06-22 14:24 UTCEPSS rescore
  24. 2026-06-21 14:55 UTCEPSS rescore
  25. 2026-06-21 01:58 UTCEPSS rescore
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  27. 2026-06-19 19:24 UTCEPSS rescore
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  29. 2026-06-18 17:51 UTCEPSS rescore
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  31. 2026-06-17 17:51 UTCEPSS rescore
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  41. 2026-06-12 23:10 UTCEPSS rescore
  42. 2026-06-12 08:06 UTCOSV refresh
  43. 2026-06-11 13:58 UTCEPSS rescore
  44. 2026-06-11 13:58 UTCEPSS rescore
  45. 2026-06-10 22:16 UTCEPSS rescore
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  48. 2026-06-08 14:15 UTCEPSS rescore
  49. 2026-06-08 14:15 UTCEPSS rescore
  50. 2026-06-07 15:23 UTCEPSS rescore
  51. 2026-06-07 15:23 UTCEPSS rescore
  52. 2026-06-06 13:46 UTCEPSS rescore
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  54. 2026-06-05 22:45 UTCEPSS rescore
  55. 2026-06-05 06:09 UTCEPSS rescore
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  72. 2026-05-26 07:17 UTCEPSS rescore
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  74. 2026-05-26 07:17 UTCEPSS rescore
  75. 2026-05-26 02:15 UTCEG score recompute

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Frequently asked(5)

What is CVE-2021-3631?
CVE-2021-3631 is a medium vulnerability published on March 2, 2022. 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…
When was CVE-2021-3631 disclosed?
CVE-2021-3631 was first published in the National Vulnerability Database on March 2, 2022, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-3631 actively exploited?
CVE-2021-3631 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 39.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-3631?
CVE-2021-3631 has a CVSS v3 base score of 6.3 (NVD).
How do I remediate CVE-2021-3631?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-3631, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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