CVE-2021-3995

MEDIUMNVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.5 under NVD CVSS v3. EPSS exploit probability: 0.6%, top 54% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this week
5.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 5.5Exploit: NoneExposed: 0

A fix is available — apply it.

A logic error was found in the libmount library of util-linux in the function that allows an unprivileged user to unmount a FUSE filesystem. This flaw allows an unprivileged local attacker to unmount FUSE filesystems that belong to certain other users who have a UID that is a prefix of the UID of the attacker in its string form. An attacker may use this flaw to cause a denial of service to applications that use the affected filesystems.

CVSS v3
5.5
EG Score
5.5(medium)
EG Risk
30(Track)
EG Risk 30/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity55% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
46.5%
KEV
Not listed

Published

August 23, 2022

Last Modified

November 21, 2024

References (18)

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibuuid1 (2.34-0.1ubuntu9.3) @ focal2026-05-25ubuntu

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.

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 13× in last 7d / 51× 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 107 total refreshes for this CVE.

  1. 2026-07-23 02:04 UTCEG score recompute
  2. 2026-07-22 22:50 UTCEG score recompute
  3. 2026-07-22 14:06 UTCEPSS rescore
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  48. 2026-06-11 13:55 UTCOSV refresh
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Frequently asked(5)

What is CVE-2021-3995?
CVE-2021-3995 is a medium vulnerability published on August 23, 2022. A logic error was found in the libmount library of util-linux in the function that allows an unprivileged user to unmount a FUSE filesystem. This flaw allows an unprivileged local attacker to unmount FUSE filesystems that belong to certain other users who have a UID that is a prefix of the UID of…
When was CVE-2021-3995 disclosed?
CVE-2021-3995 was first published in the National Vulnerability Database on August 23, 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-2021-3995 actively exploited?
CVE-2021-3995 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 46.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-3995?
CVE-2021-3995 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2021-3995?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-3995, 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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