CVE-2021-33910

Local crash via excessive stack allocation

Published Jul 20, 2021 · Updated Jun 9, 2025

Memory allocation flaw in systemd before 246.15, 247.8, 248.5, and 249.1 allows local users to crash the operating system. The basic/unit-name.c path handling uses strdupa and alloca on an attacker-controlled pathname, exhausting the stack while constructing a unit name. Local users able to provide a sufficiently long pathname can trigger a systemd or PID 1 crash, producing an availability-only service interruption.

CVSS severity5.5
Medium
EPSS probability8.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory allocation flaw in systemd before 246.15, 247.8, 248.5, and 249.1 allows local users to crash the operating system. The basic/unit-name.c path handling uses strdupa and alloca on an attacker-controlled pathname, exhausting the stack while constructing a unit name. Local users able to provide a sufficiently long pathname can trigger a systemd or PID 1 crash, producing an availability-only service interruption.

The record

CVE
CVE-2021-33910
Published
Jul 20, 2021
Updated
Jun 9, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-770, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5NVDCVSS: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

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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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 exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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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