CVE-2021-3996 Missing authorization in util-linux

What is CVE-2021-3996?

CVE-2021-3996 is a medium-severity missing authorization vulnerability in Fedoraproject Fedora, published on 23 Aug 2022. It can only be exploited from the same machine or local network, with no action from the victim.

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.

Weakness: CWE-552

Which versions are affected by CVE-2021-3996?

It affects 2 products.

Products include Fedoraproject Fedora, Kernel Util-Linux.

How do I fix CVE-2021-3996?

Apply the vendor's patch.

Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.

Is CVE-2021-3996 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-3996 exists.

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All Fedoraproject Fedora vulnerabilities

Sources

• CVE record
• NVD
• OSV
• How this page is made

Also known as ALPINE-CVE-2021-3996, CLEANSTART-2026-GD03162, DEBIAN-CVE-2021-3996, JLSEC-2025-193, UBUNTU-CVE-2021-3996.