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NVD / CVE Program· CNA redhat

CVE-2021-3995: 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.

MediumCVSS 5.5 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.63% (FIRST EPSS); higher than 51% of all records.
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: util-linux (Alpine:v3.12) 2.37.3-r0; util-linux (Debian:11) 2.36.1-8+deb11u1; util-linux (Debian:12) 2.37.3-1.
  • Mentioned 2 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to util-linux (Alpine:v3.12) 2.37.3-r0; util-linux (Debian:11) 2.36.1-8+deb11u1; util-linux (Debian:12) 2.37.3-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
Aug 23, 2022
Updated
Jun 17, 2026
EPSS
0.6% · 51th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.6%

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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  • when exploit code appears or is weaponized
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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
kernelutil-linux
fedoraprojectfedora

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a util-linux

    • Fixed in util-linux v2.37.3affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • fedoraproject fedora35
  • kernel util-linux2.34 and later · before 2.37.3

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Alpine:v3.12util-linuxfrom 2.34 · before 2.37.3-r02.37.3-r0
Debian:11util-linuxbefore 2.36.1-8+deb11u12.36.1-8+deb11u1
Debian:12util-linuxbefore 2.37.3-12.37.3-1
openSUSE:Leap 15.3libeconfbefore 0.4.4+git20220104.962774f-150300.3.6.20.4.4+git20220104.962774f-150300.3.6.2
openSUSE:Leap 15.3python3-libmountbefore 2.36.2-150300.4.14.22.36.2-150300.4.14.2
openSUSE:Leap 15.3shadowbefore 4.8.1-150300.4.3.84.8.1-150300.4.3.8
openSUSE:Leap 15.3util-linuxbefore 2.36.2-150300.4.14.32.36.2-150300.4.14.3
openSUSE:Leap 15.3util-linux-systemdbefore 2.36.2-150300.4.14.22.36.2-150300.4.14.2
openSUSE:Tumbleweedutil-linuxbefore 2.37.3-1.12.37.3-1.1
SUSE:Linux Enterprise Module for Basesystem 15 SP3libeconfbefore 0.4.4+git20220104.962774f-150300.3.6.20.4.4+git20220104.962774f-150300.3.6.2
SUSE:Linux Enterprise Module for Basesystem 15 SP3shadowbefore 4.8.1-150300.4.3.84.8.1-150300.4.3.8
SUSE:Linux Enterprise Module for Basesystem 15 SP3util-linuxbefore 2.36.2-150300.4.14.32.36.2-150300.4.14.3
SUSE:Linux Enterprise Module for Basesystem 15 SP3util-linux-systemdbefore 2.36.2-150300.4.14.22.36.2-150300.4.14.2

Same product

kernel: all records

Other highest-scoring records for the same primary product.

  • CVE-2015-5224The mkostemp function in login-utils in util-linux when used incorrectly allows remote attackers to cause file name collision and possibly…
    40Plan
  • CVE-2018-7738In util-linux before 2.32-rc1, bash-completion/umount allows local users to gain privileges by embedding shell commands in a mountpoint…
    31Monitor
  • CVE-2016-2779runuser in util-linux allows local users to escape to the parent session via a crafted TIOCSTI ioctl call, which pushes characters to the…
    31Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-37600Jul 30, 2021 · An integer overflow in util-linux through 2.37.1 can potentially cause a buffer overflow if an attacker were able to use system resources…
    22Monitor
  • ← EarlierCVE-2022-0563Feb 21, 2022 · A flaw was found in the util-linux chfn and chsh utilities when compiled with Readline support.
    22Monitor
  • Later →CVE-2021-3996Aug 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.
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
alpine:util-linux2.37.3-r0 · Alpine:v3.12Package registry (OSV)
debian:util-linux2.37.3-1 · Debian:12Package registry (OSV)
opensuse:libeconf0.4.4+git20220104.962774f-150300.3.6.2 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:python3-libmount2.36.2-150300.4.14.2 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:shadow4.8.1-150300.4.3.8 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:util-linux2.36.2-150300.4.14.3 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:util-linux-systemd2.36.2-150300.4.14.2 · openSUSE:Leap 15.3Package registry (OSV)
suse:libeconf0.4.4+git20220104.962774f-150300.3.6.2 · SUSE:Linux Enterprise Module for Basesystem 15 SP3Package registry (OSV)
suse:shadow4.8.1-150300.4.3.8 · SUSE:Linux Enterprise Module for Basesystem 15 SP3Package registry (OSV)
suse:util-linux2.36.2-150300.4.14.3 · SUSE:Linux Enterprise Module for Basesystem 15 SP3Package registry (OSV)
suse:util-linux-systemd2.36.2-150300.4.14.2 · SUSE:Linux Enterprise Module for Basesystem 15 SP3Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: EPSS history · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-552 · Files or Directories Accessible to External Parties

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records