HOMEVULNERABILITIESCVE-2021-3996
MEDIUM

CVE-2021-3996

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 a local user on a vulnerable system to unmount other users' filesystems that are either world-writable themselves (like /tmp) or mounted in a world-writable directory. An attacker may use this flaw to cause a denial of service to applications that use the affected filesystems.

NVD Source

Technical Analysis

CVE-2021-3996 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
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://bugzilla.redhat.com/show_bug.cgi?id=2024628
PATCHhttps://github.com/util-linux/util-linux/commit/166e87368ae88bf31112a30e078cceae637f4cdb
PATCHhttps://www.openwall.com/lists/oss-security/2022/01/24/2
PATCHhttps://bugzilla.redhat.com/show_bug.cgi?id=2024628
PATCHhttps://github.com/util-linux/util-linux/commit/166e87368ae88bf31112a30e078cceae637f4cdb
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://access.redhat.com/security/cve/CVE-2021-3996
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://access.redhat.com/security/cve/CVE-2021-3996
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 (20)

→
http://packetstormsecurity.com/files/170176/snap-confine-must_mkdir_and_open_with_perms-Race-Condition.htmlThird Party Advisory
→
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://access.redhat.com/security/cve/CVE-2021-3996Issue Tracking · Third Party Advisory
→
https://bugzilla.redhat.com/show_bug.cgi?id=2024628Issue Tracking · Patch · Third Party Advisory
→
https://github.com/util-linux/util-linux/commit/166e87368ae88bf31112a30e078cceae637f4cdbPatch · 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/Broken Link · 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
→
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://access.redhat.com/security/cve/CVE-2021-3996Issue Tracking · Third Party Advisory
→
https://bugzilla.redhat.com/show_bug.cgi?id=2024628Issue Tracking · Patch · Third Party Advisory

Quick Facts

CVE IDCVE-2021-3996
CVSS Score5.5 / 10
SeverityMEDIUM
WeaknessCWE-552
CISA KEVNo
Affected2 vendor(s)
PublishedAug 23, 2022

Related CVEs (CWE-552)

CVE-2025-41240
10.0
CVE-2025-14771
9.9
CVE-2024-39931
9.9
CVE-2024-53676
9.8
CVE-2017-14942
9.8
CVE-2024-39581
9.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-3996 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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