CVE-2021-3997

Exp

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.

Published: 2022-08-23 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-3997 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.02%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-3997

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-3997

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-11-21 0.08% 0.02% -0.06%
2 2025-11-18 0.02% 0.08% +0.06%
3 2025-10-16 — 0.02% —

Full EPSS history (8 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3997

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]

Weakness enumeration for CVE-2021-3997

OS Trackers for CVE-2021-3997

vendor priority summary link
debian not yet assigned CVE-2021-3997 not yet assigned priority: Debian including 1 source packages (systemd), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-3997
gentoo normal CVE-2021-3997: 1 GLSA(s) (202305-15), 4 atom(s) (sys-apps/systemd, sys-apps/systemd-tmpfiles, sys-apps/systemd-utils, sys-fs/udev); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-3997
redhat medium — https://access.redhat.com/security/cve/CVE-2021-3997
suse medium CVE-2021-3997 severity moderate: SUSE including 505 source package names (0.21.0.3.2.10:libsystemd0-246.16-7.33.1, 0.21.0.3.2.10:libudev1-246.16-7.33.1, …), 1111 product×package rows across 136 product lines (Container bci/bci-init, Container bci/dotnet-aspnet, … (136 product lines)): Fixed 581, Known Not Affected 352, Known Affected 178. https://www.suse.com/security/cve/CVE-2021-3997/
ubuntu medium CVE-2021-3997 medium priority: Ubuntu including 1 source packages (systemd), 7 status rows across 7 suites (bionic, focal, hirsute, impish, trusty, upstream, xenial): ignored 3, released 3, needs-triage 1. https://ubuntu.com/security/CVE-2021-3997

Affected software / configurations for CVE-2021-3997

Vendor Product Version Raw CPE
systemd_project systemd >= 240, < 250.2 cpe:2.3:a:systemd_project:systemd:*:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
redhat enterprise_linux 7.0 cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
redhat enterprise_linux 9.0 cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:*

References for CVE-2021-3997

cvelogic Threat Intelligence