CVE-2021-42379Network attack vector

Denial of service via next_input_file use-after-free

Published Nov 15, 2021 · Updated Nov 3, 2025

Use-after-free in BusyBox awk 1.18.0 through 1.33.1 allows attackers to crash the process via a crafted awk pattern. The next_input_file function continues to access freed memory while processing the attacker-controlled pattern. Execution requires the awk applet to be compiled in and invoked on the pattern; the documented outcome is a process crash, with code execution reported as possible rather than confirmed.

CVSS severity7.2
High
EPSS probability2.77%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in BusyBox awk 1.18.0 through 1.33.1 allows attackers to crash the process via a crafted awk pattern. The next_input_file function continues to access freed memory while processing the attacker-controlled pattern. Execution requires the awk applet to be compiled in and invoked on the pattern; the documented outcome is a process crash, with code execution reported as possible rather than confirmed.

The record

CVE
CVE-2021-42379
Published
Nov 15, 2021
Updated
Nov 3, 2025
Vendor
BusyBox
Product
BusyBox
Classifications
CWE-416
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Nov 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 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?

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

  1. Affected versionversion=unspecified <1.34.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

BusyBox · BusyBoxversion=unspecified <1.34.0

Published CVSS scores

7.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
7.2CISA-ADPCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
6.6Amazon LinuxCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

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

Weakness, pattern, technique

CWE-416Use After Free

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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