CVE-2021-3997: A flaw was found in systemd

Q: How do I fix CVE-2021-3997?

systemd: upgrade to 250.2; fedora: mitigate or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-3997 being exploited?

CVE-2021-3997 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-3997 affect?

CVE-2021-3997 affects systemd, fedora, enterprise linux. Severity is medium (CVSS 5.5). 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.

Q: How urgent is CVE-2021-3997?

Priority 49/100. Public exploit reference; On your watchlist

This month

MEDIUM 5.5WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-3997 is a medium-severity flaw (CVSS 5.5) affecting systemd, fedora, enterprise linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	1.7% (top 22%)
CISA exploited list	No
Weakness	CWE-674
Published	2022-08-23
Last modified	2026-11-02

Publisher (CNA): Red Hat, Inc. · Vendor: fedoraproject · redhat · systemd project

Last updated 2026-11-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-08-23 20:15 UTCPublished CVE record published
2026-11-02 19:17 UTCUpdated Record last modified

systemd project systemd UPGRADE

Affected: >= 240 and < 250.2

Fixed in: 250.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy systemd || rpm -q systemd || systemd --version

2. UPGRADE to 250.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade systemd

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade systemd

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

fedoraproject fedora MITIGATE

Affected: 34 · 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 34

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux MITIGATE

Affected: 7.0 · 8.0 · 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-3997?

systemd: upgrade to 250.2; fedora: mitigate or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-3997 being exploited?

CVE-2021-3997 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-3997 affect?

CVE-2021-3997 affects systemd, fedora, enterprise linux. Severity is medium (CVSS 5.5). 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.

How urgent is CVE-2021-3997?

Priority 49/100. Public exploit reference; On your watchlist

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References

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