CVE-2021-3996

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.

• CWE-552
• CWE-552

• 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
• 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

Published

Aug 23, 2022

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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