CVE-2021-3997Public exploit

Boot-time service disruption via recursive directory removal

Published Aug 23, 2022 · Updated Aug 3, 2024

Uncontrolled recursion in systemd-tmpfiles 240 through 250.1 allows local users to crash boot-time temporary-file processing. The rm_rf_children function recursively descends each attacker-created directory under /tmp until stack exhaustion terminates systemd-tmpfiles. Exploitation requires local directory creation before boot cleanup; the crash prevents the subsequent creation phase and can leave required runtime paths absent.

CVSS severity5.5
Medium
EPSS probability1.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled recursion in systemd-tmpfiles 240 through 250.1 allows local users to crash boot-time temporary-file processing. The rm_rf_children function recursively descends each attacker-created directory under /tmp until stack exhaustion terminates systemd-tmpfiles. Exploitation requires local directory creation before boot cleanup; the crash prevents the subsequent creation phase and can leave required runtime paths absent.

The record

CVE
CVE-2021-3997
Published
Aug 23, 2022
Updated
Aug 3, 2024
Vendor
systemd
Product
systemd
Classifications
CWE-674, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 23, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Fixed in v251-rc1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

systemd · systemdversion=Fixed in v251-rc1

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-674Uncontrolled Recursion
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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