HOME VULNERABILITIESCVE-2021-3995

MEDIUM

CVE-2021-3995

CWE-552Published: August 23, 2022· Updated: Jun 17, 2026

5.5

CVSS v3.1

Official Description

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.

Technical Analysis

CVE-2021-3995 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 5.5.

CVSS v3.1 Vector Breakdown

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges Req.Low

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Affected Vendors & Products

Fedora1 product(s)

fedora

kernel1 product(s)

util-linux

Source: NVD CPE · 2 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time

Offensive Security exploit database

GitHub PoC Search

Community PoC repositories

Rapid7 / Metasploit

Metasploit module search

Security advisories & exploits

Official NIST entry

CVE Program entry

External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/util-linux/util-linux/commit/57202f5713afa2af20ffbb6ab5331481d0396f8d

PATCHhttps://www.openwall.com/lists/oss-security/2022/01/24/2

PATCHhttps://github.com/util-linux/util-linux/commit/57202f5713afa2af20ffbb6ab5331481d0396f8d

PATCHhttps://www.openwall.com/lists/oss-security/2022/01/24/2

ADVISORYhttp://packetstormsecurity.com/files/170176/snap-confine-must_mkdir_and_open_with_perms-Race-Condition.html

ADVISORYhttp://seclists.org/fulldisclosure/2022/Dec/4

ADVISORYhttp://www.openwall.com/lists/oss-security/2022/11/30/2

ADVISORYhttps://mirrors.edge.kernel.org/pub/linux/utils/util-linux/v2.37/v2.37.3-ReleaseNotes

ADVISORYhttps://security.netapp.com/advisory/ntap-20221209-0002/

ADVISORYhttp://packetstormsecurity.com/files/170176/snap-confine-must_mkdir_and_open_with_perms-Race-Condition.html

ADVISORYhttp://seclists.org/fulldisclosure/2022/Dec/4

ADVISORYhttp://www.openwall.com/lists/oss-security/2022/11/30/2

ADVISORYhttps://mirrors.edge.kernel.org/pub/linux/utils/util-linux/v2.37/v2.37.3-ReleaseNotes

ADVISORYhttps://security.netapp.com/advisory/ntap-20221209-0002/

All References (18)

→

http://packetstormsecurity.com/files/170176/snap-confine-must_mkdir_and_open_with_perms-Race-Condition.htmlThird Party Advisory · VDB Entry

→

http://seclists.org/fulldisclosure/2022/Dec/4Mailing List · Third Party Advisory

→

http://www.openwall.com/lists/oss-security/2022/11/30/2Mailing List · Third Party Advisory

→

https://bugzilla.redhat.com/show_bug.cgi?id=2024631https://access.redhat.com/security/cve/CVE-2021-3995Broken Link · Issue Tracking

→

https://github.com/util-linux/util-linux/commit/57202f5713afa2af20ffbb6ab5331481d0396f8dPatch · Third Party Advisory

→

https://mirrors.edge.kernel.org/pub/linux/utils/util-linux/v2.37/v2.37.3-ReleaseNotesRelease Notes · Vendor Advisory

→

https://security.gentoo.org/glsa/202401-08

→

https://security.netapp.com/advisory/ntap-20221209-0002/Third Party Advisory

→

https://www.openwall.com/lists/oss-security/2022/01/24/2Exploit · Mailing List · Patch · Third Party Advisory

→

http://packetstormsecurity.com/files/170176/snap-confine-must_mkdir_and_open_with_perms-Race-Condition.htmlThird Party Advisory · VDB Entry

→

http://seclists.org/fulldisclosure/2022/Dec/4Mailing List · Third Party Advisory

→

http://www.openwall.com/lists/oss-security/2022/11/30/2Mailing List · Third Party Advisory

→

https://bugzilla.redhat.com/show_bug.cgi?id=2024631https://access.redhat.com/security/cve/CVE-2021-3995Broken Link · Issue Tracking

→

https://github.com/util-linux/util-linux/commit/57202f5713afa2af20ffbb6ab5331481d0396f8dPatch · Third Party Advisory

→

https://mirrors.edge.kernel.org/pub/linux/utils/util-linux/v2.37/v2.37.3-ReleaseNotesRelease Notes · Vendor Advisory

Quick Facts

CVE IDCVE-2021-3995

CVSS Score5.5 / 10

SeverityMEDIUM

WeaknessCWE-552

CISA KEVNo

Affected2 vendor(s)

PublishedAug 23, 2022

Related CVEs (CWE-552)

Recommended Actions

→Apply vendor patches immediately
→Monitor CVE-2021-3995 in threat intel feeds
→Review IDS/IPS signatures for exploitation attempts

Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.

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