CVE-2021-3997 Denial of service in systemd

Medium 5.5 Published 23 Aug 2022 Updated 14 Oct 2026

An attacker can cause a denial of service at boot time by creating excessive nested directories in /tmp, affecting systemd-tmpfiles.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2021-3997?

CVE-2021-3997 is a medium-severity denial of service 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 flaw was found in systemd. An uncontrolled recursion in systemd-tmpfiles may lead to a denial of service at boot time when too many nested directories are created in /tmp.

Weakness: CWE-674

Which versions are affected by CVE-2021-3997?

It affects 3 products.

Linux distribution packages (9)

`systemd` SUSE:Linux Enterprise Micro 5.1	All versions	`246.16-150300.7.39.1`
`systemd` SUSE:Linux Enterprise Micro 5.1	All versions	`246.16-7.33.1`
`systemd` SUSE:Linux Enterprise Module for Basesystem 15 SP3	All versions	`246.16-150300.7.39.1`
`systemd` SUSE:Linux Enterprise Module for Basesystem 15 SP3	All versions	`246.16-7.33.1`
`htmldoc` SUSE:Package Hub 15 SP3	All versions	`1.9.12-bp153.2.6.1`
`htmldoc` openSUSE:Leap 15.3	All versions	`1.9.12-bp153.2.6.1`
`systemd` openSUSE:Leap 15.3	All versions	`246.16-150300.7.39.1`
`systemd` openSUSE:Leap 15.3	All versions	`246.16-7.33.1`
`systemd` openSUSE:Tumbleweed	All versions	`249.7-3.1`

Products include Fedoraproject Fedora, Redhat Enterprise Linux, Systemd Project Systemd.

How do I fix CVE-2021-3997?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-3997 being exploited?

There is no known exploitation of CVE-2021-3997 in the wild and no public exploit code.

All Fedoraproject Fedora vulnerabilities

Sources

Also known as AZL-10638, DEBIAN-CVE-2021-3997, GHSA-4p54-q58q-8mpc, MGASA-2022-0016, OESA-2022-1503, SUSE-SU-2022:0043-1 and 6 more.